Vaccines doi: 10.3390/vaccines14060520

Authors: Chen Chen Yuanfei Zhu Huiting Wang Fei Wu Youhua Xie Qingqing Jia Yang Yang Jiangjiang Lyu Junqiang Qu Qiao Wang Fan Wu

Background: SARS-CoV-2 reinfections increased substantially after the emergence of Omicron variants. Methods: We conducted a cross-sectional study of 2095 individuals with prior Omicron BA.2 infection in Shanghai, China, during the early post-zero-COVID period. Data on demographics, infection history, and lifestyle factors were collected via questionnaire, and blood samples were obtained for ancestral RBD-blocking antibody measurement. Results: Meeting WHO physical activity recommendations (≥600 MET-min/week) was associated with lower reinfection odds (OR = 0.59, 95% CI: 0.46–0.74, p < 0.001). The overall median ancestral RBD-blocking antibody level was 263.93 U/mL (IQR: 36.41–331.87). Older age was associated with lower ancestral RBD-blocking antibody levels (β = –0.0038 per year, 95% bootstrap CI: –0.0057 to –0.0019, p < 0.001). All vaccinated groups had significantly higher ancestral RBD-blocking antibody levels than unvaccinated individuals: partially vaccinated (β = 0.4440, 95% CI: 0.1569 to 0.6830, p < 0.001), fully vaccinated (β = 0.8516, 95% CI: 0.7464 to 0.9595, p < 0.001), homologous booster (β = 1.0297, 95% CI: 0.9408 to 1.1223, p < 0.001), and heterologous booster (β = 1.0838, 95% CI: 0.9387 to 1.2226, p < 0.001). Time since last immune event was inversely associated with ancestral RBD-blocking antibody levels (β = –0.0232 per month, 95% CI: –0.0385 to –0.0077, p = 0.0031). Conclusions: In this cross-sectional study, meeting WHO physical activity recommendations was associated with 41% lower odds of SARS-CoV-2 reinfection, although reverse causality cannot be ruled out. All vaccinated groups had higher ancestral RBD-blocking antibody levels than unvaccinated individuals. Older age and longer time since last immune event were associated with lower ancestral RBD-blocking antibody levels. These associations need confirmation in prospective, well-powered studies.

Vaccines doi: 10.3390/vaccines14060519

Authors: María Alicia Delfino Jimena Borgo Luciano Chaneton Natacha Cerny Augusto Ernesto Bivona Pierre Gsell Fernando Lobos Ike James Martin Friede German Sánchez Alberti Andrés Sánchez Alberti

The global expansion of highly pathogenic avian influenza A (H5N1), particularly the clade 2.3.4.4b lineage, has renewed urgent concerns about its pandemic potential in the context of its ongoing panzootic expansion and increasing cross-species transmission. Despite decades of preparedness initiatives, critical technological and structural gaps persist, especially in low- and middle-income countries (LMICs), where both vaccine access and sustainable manufacturing capacity remain limited. In this perspective, we examine key lessons from past influenza pandemics and global preparedness strategies, including the Global Action Plan for Influenza Vaccines, highlighting persistent challenges related to sustainable manufacturing capacity and equitable vaccine access. Additionally, we examine the potential of messenger RNA (mRNA) vaccine platforms to address these limitations, given their rapid design, scalable manufacturing, and adaptability to emerging pathogens. Moreover, we examine the role of neuraminidase (NA) as a complementary antigen capable of broadening immune protection and reducing viral transmission. Finally, we describe recent advances in Latin America, focusing on Argentina’s participation in the mRNA Technology Transfer Programme co-led by the World Health Organization (WHO) and the Medicines Patent Pool (MPP), as a model for strengthening regional manufacturing capacity and contributing to global pandemic preparedness. Together, these elements indicate that effective H5N1 pandemic preparedness will require the integration of improved antigen design, flexible mRNA platforms, and sustainable regional manufacturing systems aligned with global procurement strategies.

Vaccines doi: 10.3390/vaccines14060518

Authors: Jiannan Li Guangyu Qi Mingyue Cao Zixian Wang Gejin Lu Xulong Lang Feng Wei Tiancheng Lu Lingwei Zhu Xiuran Wang

Background: This study aimed to construct a recombinant Pseudomonas aeruginosa outer membrane vesicle (OMV) vector vaccine delivering pcrV and compare the immunological impacts of OMVs as carriers versus as adjuvants. Methods: The recombinant plasmid pBBRMCS5-pcrV was constructed and transformed into P. aeruginosa. Recombinant OMVs (OMVPcrV) were prepared via ultracentrifugation and characterized in terms of their morphology and particle size by means of transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). After a biosafety evaluation, mice were intramuscularly immunized with PcrV or OMVPcrV, followed by a booster immunization on day 21. On day 42, the mice were challenged subcutaneously and intranasally with PAO1. Bacterial loads in tissues and blood, pulmonary T-cell subsets, and serum antibody levels were assessed. Results: The recombinant plasmid was successfully constructed, and Western blotting confirmed the delivery of PcrV into OMVs. TEM revealed typical spherical nanostructures, and NTA showed a median particle size of 127.4 ± 5.3 nm. Upon subcutaneous challenge, the OMV, OMVPcrV, and OMV + PcrV groups all achieved 100% protection. Both the OMVPcrV and OMV + PcrV groups exhibited increased CD4+ and CD8+ T-cell counts and higher induction levels of specific IgM, IgG1, and IgG2a antibodies. The OMVPcrV group showed superior clearance of respiratory bacterial colonization and reduced inflammatory injury compared with the PBS control group. Conclusions: The constructed vector successfully delivered the PcrV antigen, and the OMVPcrV vaccine induced effective immune responses. Compared with wild-type outer membrane vesicles (OMVs) and the strategy of directly mixing free PcrV antigen with OMVs (OMV + PcrV), the recombinant OMVPcrV vaccine exhibited superior immunoprotective efficacy in terms of bacterial clearance and tissue protection, providing experimental evidence for the development of a Pseudomonas aeruginosa vaccine.

Vaccines doi: 10.3390/vaccines14060517

Authors: Juris Jansons Nikita Zrelovs Arta Spridzane Marija Nazarenko Liba Sokolovska Karina Biserova Daira Krisane Austra Breiksa-Vaivode Daria Avdoshina Beatrise Orlova Marta Petrovska Serhii Kalman Stefan Petkov Valery Ilinsky Anna Ilinskaya Jurijs Nazarovs Androniks Mitildzans Maria Isaguliants

Background: Persistent high-risk human papillomavirus (hrHPV) infection causes over 99% of cervical precancers and cancers worldwide, with HPV genotype 16 (HPV16) responsible for 50% of the cases. Latvia ranks among the top EU countries for cervical cancer incidence and mortality. In the general Latvian population, 4.2% of women are hrHPV-infected, mostly with HPV16. However, information on the circulating HPV16 isolates is missing. Objectives: To study the genomic variability of the Latvian HPV16 isolates, compare them with HPV16 in Europe and across the globe, reveal features associated with the severity of cervical disease and uncover eventual sequence changes due to the national HPV vaccination. Methods: DNA was extracted from the formalin-fixed paraffin-embedded cervical tissues of women diagnosed with cervical intraepithelial neoplasia (CIN) stages I-III and squamous cell carcinoma (SCC) grades 1–3, collected between 2012 and 2024. Samples positive for HPV16 were subjected to whole genome sequencing (WGS) on the Illumina platform (n = 16) or Sanger sequencing of the E6/E7 coding region (n = 31). A consensus HPV16 sequence was generated, and single nucleotide polymorphisms (SNPs) and eventual amino acid substitutions (AAS) were analysed. Results: Complete genomes of 16 HPV16 variants were reconstructed, with 13 related to the European sublineage A1 and 3 to the sublineage A2 references. Sequences showed high conservation; still 93 non-redundant variants were identified. The highest variability was observed for the capsid protein L2, and the lowest, for oncoprotein E7. The prevalence of SNPs and AAS in the Latvian HPV16 variants, specifically in capsid protein L1, did not increase with time, showing no effect of HPV vaccination. Associations between HPV16 sequence features and severity of cervical disease were limited to AAS E6:L90V, which was significantly more common in SCC grade 2/3 than in CINII/III cases (p = 0.015). Conclusions: Highly conserved HPV16 genomes circulating in Latvia harbour a series of unique as well as common nonsynonymous SNPs with respective AAS, with one, AAS E6:L90V, associating with disease severity. No HPV vaccine escape variants were detected. Deciphering complete genomes of HPV16 from CIN and SCC cases in Latvia informs public authorities performing HPV vaccination and is useful for the management of HPV-associated cervical diseases.

Vaccines doi: 10.3390/vaccines14060516

Authors: Liying Sun Yujiao Miao Deyun Jiang Chao Liu

The magnitude and quality of adaptive immune responses are fundamentally influenced by the efficiency of antigen presentation. Traditional vaccine platforms, such as live–attenuated or inactivated pathogens, although immunogenic, often present safety concerns. Conversely, subunit vaccines, despite being safer, generally exhibit poor immunogenicity due to inadequate delivery of antigens to professional antigen–presenting cells (APCs). To address this issue, the development of innovative delivery systems has become a pivotal strategy to overcome significant biological barriers, including extracellular antigen degradation, suboptimal lymph node targeting, and inefficient cross–presentation necessary for CD8+ T cell activation. This review systematically explores recent advancements in delivery technologies aimed at enhancing antigen presentation, encompassing rationally engineered nanocarriers and sophisticated biomimetic platforms. We first examine how nanoparticle properties like size, surface charge, and ligand density affect intracellular trafficking and the transition from MHC–II to MHC–I cross–presentation. Then, we explore bioinspired systems such as extracellular vesicles, virus–like particles, and cell–membrane–coated nanoparticles that utilize natural biological traits for enhanced targeting and immune modulation. Additionally, we review new physical delivery methods like microneedle arrays and in situ electroporation for direct, minimally invasive antigen delivery to dendritic cells. Lastly, we discuss the potential of these platforms in personalized cancer vaccines and combination immunotherapies. By combining insights from materials science, immunology, and bioengineering, these next–generation delivery tools could enhance antigen presentation and transform precision vaccination and immune intervention.

Vaccines doi: 10.3390/vaccines14060515

Authors: Priscila R. Guerra Elisabeth O. Nielsen Ikhlaq H. Kana Søren K. Boldsen Vanesa García Ana Herero-Fresno Nicole B. Goecke Morten A. Nielsen Adam F. Sander John E. Olsen

Background/Objectives: Post-weaning diarrhea remains a major challenge in pig production worldwide. Enterotoxigenic Escherichia coli (ETEC) encoding fimbriae of the F4 type and producing the heat-stable enterotoxin, STb, are one of the important causes of this disease. The aim of the current study was to evaluate whether vaccination of pregnant sows with a novel capsid virus-like particle (cVLP)-based vaccine against F4 and STb (cVLP-FaeG/cVLP-STb) could enhance performance in piglets born after such vaccinated sows. Methods: A field trial was conducted in a commercial sow-to-finisher pig herd. Thirty-five sows were vaccinated twice with the cVLP-FaeG/cVLP-STb vaccine prior to farrowing, while thirty-five control sows were vaccinated twice with commercial vaccines normally used in the herd. Piglets were followed until eight weeks post-weaning to assess antibody responses, diarrhea and treatment incidences, pathogen shedding, and growth performance. Results: Piglets born from immunized sows receiving the cVLP vaccine showed significantly higher serum antibody levels against ETEC F4 throughout the post-weaning period (p ≤ 0.021). The frequency of pathogen detection was similar between groups, while piglets in the cVLP group exhibited significantly lower diarrhea scores at week 6 (p = 0.047), showed a trend of requiring fewer treatments (p = 0.06) and had significantly higher final body weight (p = 0.048). In addition, the cVLP group showed a significantly greater average daily gain over the study period (p = 0.037). Conclusion: Sow immunization with the cVLP vaccine enhanced passive immune protection of piglets, resulting in reduced antimicrobial treatment 2 weeks post-weaning and improved growth performance.

Vaccines doi: 10.3390/vaccines14060514

Authors: Francesco Manfredi Flavia Ferrantelli Chiara Chiozzini Micaela Donnini Patrizia Leone Katherina Pugliese Monica Cagiola Cecilia Righi Stefano Petrini Monica Giammarioli Francesco Feliziani Maurizio Federico

Background/Objectives: African Swine Fever (ASF) represents one of the most serious threats to animal health and global food security. The causative agent of ASF is the African swine fever virus (ASFV), a DNA virus belonging to the Asfarviridae family. Here, we describe ex vivo results for an original anti-ASFV vaccine approach based on the cellular immune response induced by extracellular vesicles (EVs) engineered to express four ASFV proteins. EV engineering was achieved by expressing a DNA vector encoding a biologically inactive HIV-1 Nef protein (Nefmut), which exhibits unusually high efficiency of incorporation into EVs, even when fused to foreign proteins. Previous studies have demonstrated that intramuscular injection of Nefmut-based vectors leads to the engineering of Evs, spontaneously released by muscle cells, and induction of antigen-specific CD8+ T cell immunity. Methods: We designed DNA vectors expressing the fusion products between Nefmut and each of the four ASFV structural proteins p30, p54, pp62, and p72. Engineered EVs were molecularly characterized by Western blot and nanotrack analysis, and their potential immunogenicity was assessed by priming and cross-presentation assays. Results: We assessed that the four fusion proteins were successfully expressed in transfected mammalian cells, with the release of valuable amounts of engineered EVs. When immature swine dendritic cells were challenged with the engineered EVs and then co-cultivated with autologous peripheral blood lymphocytes in priming assays, lymphocyte subpopulations specifically reacting against each ASFV antigen were elicited, as detected by an IFN-γ ELISpot assay. In addition, we provide evidence that the Nefmut-based fusion products incorporated into the engineered EVs can be cross-presented by professional antigen-presenting cells, leading to cross-priming of autologous lymphocytes. Conclusions: These results represent the best premise to go forward with experiments examining immunogenicity and antiviral efficiency in pigs.

Vaccines doi: 10.3390/vaccines14060513

Authors: Hongbiao Chen Sinawaer Abulimiti Miaoqi Wan Fuk-yuen Yu Yuan Fang He Cao Fengjuan Chen Jimileguli Aini Xiaoqian Deng Haiyan Yan Aynur Yusup Abuduwupur Kahar Zixin Wang

Background: Self-compassion is the practice of treating oneself with kindness and understanding during times of hardship. There is a lack of studies investigating the associations between self-compassion and vaccination behaviors. This study investigated the associations between self-compassion and behavioral intention to receive seasonal influenza vaccination (SIV), pneumococcal vaccination (PV), and respiratory syncytial virus (RSV) vaccination among community-living older adults in Western China. Methods: A cross-sectional survey was conducted among people aged ≥60 years in Kashgar, China between January and February 2026. Participants were recruited through multi-stage random sampling. Multivariable logistic regression models were fitted. Results: Among all participants, 56.5% intended to receive a fully subsidized SIV in the next year. Among those without a prior vaccination history, 48.2% and 49.7% intended to receive fully subsidized PV and RSV vaccination in the next year, respectively. After adjusting for significant background characteristics, higher levels of self-compassion (e.g., higher levels of mindfulness, self-kindness and common humanity, and lower levels of over-identification, isolation and self-judgment) were associated with higher odds of behavioral intention to receive a fully subsidized SIV, PV and/or RSV vaccination. Conclusions: Our findings suggested a new angle to promote vaccination uptake. Future studies may evaluate the efficacy of self-compassion interventions in improving vaccination uptake among older adults.

Vaccines doi: 10.3390/vaccines14060512

Authors: Yuge Wang Yingyi Chen Kaixin Wang Youqing Yuan Haojie Sun Youming Yuan Jixian Wang Zhicai Yang Yi Yang Naidong Wang Deyong Duan Aibing Wang

Background/Objectives: Canine papillomavirus (CPV) is an important viral pathogen associated with papillomatosis in dogs, with canine papillomavirus type 1 (CPV1) and type 2 (CPV2) among the most prevalent and clinically relevant genotypes. The L1 capsid protein is a major immunogenic antigen of papillomaviruses; however, conserved linear B-cell epitopes shared between CPV genotypes remain poorly defined. This study aimed to identify conserved cross-reactive B-cell epitopes within CPV1 and CPV2 L1 proteins and to evaluate their preliminary immunoreactivity. Methods: Conserved linear B-cell epitopes were predicted through integrated bioinformatic and structural analyses based on sequence conservation and surface accessibility. Three candidate epitopes were selected. Recombinant CPV1 and CPV2 L1 proteins were expressed in Escherichia coli (E. coli), purified, used as recombinant L1 antigens, together with BSA-conjugated synthetic epitope peptides for mouse immunization. Antigen-specific IgG responses were assessed by ELISA, antigen-associated IFN-γ responses were evaluated by ELISpot, and cross-reactive antibody recognition was assessed by Western blot. Results: Recombinant L1 proteins induced strong antigen-specific IgG responses in mice. The selected peptides induced detectable but weaker humoral responses compared with the recombinant L1 proteins. Among the three epitopes, TPSGSLV and TVVDNTR elicited antibodies that recognized both CPV1 and CPV2 L1 proteins, while the epitope VIVPKVS showed minimal or no detectable immunoreactivity. ELISpot analysis showed only modest antigen-associated IFN-γ responses, particularly in peptide-immunized groups. Conclusions: This study identified conserved cross-reactive linear B-cell epitope candidates within CPV1 and CPV2 L1 proteins and provided preliminary immunological evidence supporting their potential relevance for CPV antigen design. However, peptide-induced responses were weaker than those induced by recombinant L1 proteins, and VLP formation, antibody neutralizing activity, and protective efficacy were not evaluated. Further studies in dogs, including optimized antigen-display platforms, neutralization assays, and protection studies, are required to determine the practical value of these epitopes for CPV vaccine development.

Vaccines doi: 10.3390/vaccines14060511

Authors: Weronika Marta Balas Maja Kaczor Joanna Strzelecka Adam Jerzy Sybilski

Background: Measles has re-emerged in recent years as a public health concern in the context of insufficient vaccination coverage. Some children experience significant delays in receiving, or refuse to take, the measles, mumps and rubella (MMR) vaccination, often due to concerns related to hen’s egg allergy (HEA). Methods: In this study, we retrospectively assessed the safety of MMR vaccination (Priorix®, GlaxoSmithKline, Belgium) in patients with HEA hospitalised at our clinic. Detailed medical histories were collected, along with skin prick tests and measurements of specific IgE against milk and egg proteins or extracts. The study included 39 patients with a mean age of 19 months, of whom 15 had previously experienced an anaphylactic reaction after egg ingestion. Results: None of these patients experienced a systemic reaction to vaccination. One patient developed a generalised maculopapular rash, which resolved after a single dose of an antihistamine. Vaccination was postponed in 63% of patients, with the longest delay extending to 113 months. Conclusions: Severe adverse reactions following MMR vaccination in patients with HEA are generally rare and are outweighed by the risks associated with natural infection and its complications. Effective communication of vaccine safety data and strengthening public trust in healthcare professionals are crucial.

Vaccines doi: 10.3390/vaccines14060510

Authors: Jun Ge Kangwei Xu Yong Cao Jiaojiao Sun Lili Guo Lilong Sun Ke Liu Jinbiao Lu Jianqiang Li Yixuan Zhang

Developing potent adjuvants is critical for enhancing vaccine efficacy, particularly for subunit antigens. Background/Objectives: This study evaluates a novel composite adjuvant system combining liposomal QS-21 and CpG ODNs to enhance vaccine-induced immunogenicity, particularly Th1-type cellular immunity. Methods: To mitigate QS-21’s hemolytic toxicity and ensure precision delivery, a stable liposomal formulation was developed. Mice models were established using varicella-zoster virus (VZV) glycoprotein E (gE) or ovalbumin (OVA) as antigens to evaluate humoral and cellular immune responses. Results: Immunization with gE protein formulated with this novel adjuvant synergistically triggered robust immune responses, outperforming single adjuvants and the combination of QS-21/MPL. Across broad dose ranges, it induced higher Th1-type cellular immunity and comparable humoral immunity relative to AS01B. Mechanistic studies revealed that the adjuvant significantly enhances the recruitment of dendritic cells (DCs), monocytes, and neutrophils to draining lymph nodes (dLNs) while upregulating co-stimulatory molecules CD40 and CD86 on DCs. Furthermore, the formulation triggered robust, transient increases in Th1-associated cytokines (IFN-γ, IL-12) and chemokines (CXCL9, CXCL10) across the injection site, serum, and dLNs. Conclusions: These findings indicate that the liposomal QS-21 and CpG ODNs system is a highly effective platform for promoting robust Th1-biased immunity, offering a promising adjuvant candidate and a solid experimental foundation for developing next-generation vaccines requiring potent cellular immunity.

Vaccines doi: 10.3390/vaccines14060507

Authors: Zhuang Li Yuan Zhang Yiyang Zheng Hongyu Wang Chenyang Xu Qing He

Therapeutic vaccines are a key strategy to achieve the goal of “functional cure” of chronic viral infections, including hepatitis B virus (HBV), hepatitis C virus (HCV), human immunodeficiency virus (HIV), human papillomavirus (HPV), and Epstein–Barr virus (EBV). Various platforms (such as viral vectors, nucleic acid vaccines, recombinant proteins, etc.) have successfully induced strong virus-specific T-cell responses in early trials, but their clinical efficacy is still limited by the immunosuppressive environment formed by the host. The core bottlenecks are severe T-cell exhaustion, viral immune escape, and various forms of local immune tolerance. Therefore, the field is moving toward combination therapies, including reduction of viral load, targeting of immune activation, and inhibition of inhibitory signaling pathways. This article summarizes the preclinical and clinical progress of therapeutic vaccines in the past decade, analyzes the major challenges in vaccine development, and discusses the future development directions in this field.

Vaccines doi: 10.3390/vaccines14060509

Authors: Marco Polo Peralta Alvarez Shawkat Hussain Andrea Magri Jacqueline Vieira Cheelsea Pereira Faith Vinluan Matteo N. Barbaglia Daniel Wright Susan J. Morris Emma Bolam Eleanor Berrie Teresa Lambe Tanja Brenner Richard Tarrant Sarah C. Gilbert Catherine M. Green Alexander D. Douglas

Background: Adenovirus-vectored vaccines played an important role in the global response to SARS-CoV-2. Adenovirus platforms have many advantages including a simple and readily transferred manufacturing process, low cost, and thermostability. Speed of production of an initial Good Manufacturing Practice (GMP)-compliant batch has, however, been viewed as a limitation of adenovirus vectors relative to mRNA platforms. Production of the initial viral starting material and release testing are key rate-limiting steps. Methods: Production of viral starting material from DNA, and release testing in accordance with regulatory expectations, for first-in-human trials of adenovirus-vectored vaccines. Results: We describe experience of these stages in the production of the first GMP batches for multiple adenovirus-vectored candidates and the adaptations made for ChAdOx1 nCoV-19 (the Oxford COVID-19 vaccine) in early 2020. We also report development of a streamlined approach to starting material generation, enabling initial GMP batch availability within c. 60 days of publication of a new pathogen sequence. Using a New World arenavirus vaccine construct as a proof of concept, we demonstrate reproducible execution of this pipeline, maintaining acceptable infectivity and other quality attributes. Conclusions: We discuss opportunities for additional time savings in the future. This work demonstrates suitability of an adenovirus platform to contribute to the “100 Days Mission” for vaccines against “Disease X”.

Vaccines doi: 10.3390/vaccines14060508

Authors: Swarandeep Singh Surabhi Gautam Vidhi Thakkar Sanjeev Kumar Devyani Joshi

Vaccination remains one of the most effective strategies for preventing infectious diseases. Yet, the success of modern vaccines increasingly depends on the rational design of adjuvants that enhance and shape immune responses. In this review, we examine current and emerging adjuvant strategies for viral vaccines across the human lifespan. Traditional adjuvants, particularly aluminum salts, have long served as the foundation of vaccine formulations. Still, their limitations have driven the exploration of novel platforms, including emulsions, nucleic acid-based adjuvants, and advanced particulate delivery platforms with intrinsic immunostimulatory properties. These newer approaches act through diverse mechanisms, such as activating innate immune pathways via pattern recognition receptors (PRRs) and stimulating antigen-presenting cells (APCs), thereby improving both humoral and cellular immunity. Recent advances in molecular biology, nanotechnology, and systems vaccinology have deepened mechanistic understanding and enabled more precise modulation of immune responses. However, significant challenges remain, including incomplete knowledge of adjuvant mechanisms, limited diversity among licensed adjuvants, safety concerns, and inconsistent efficacy across age groups. In particular, immune immaturity in infants and immunosenescence in older adults highlight the need for age-specific adjuvant strategies. The review identifies critical gaps in comparative studies, long-term safety data, and the development of adjuvants capable of inducing broad and durable immunity. Further, this article integrates licensed and emerging viral vaccine adjuvants through a lifespan framework. Addressing these limitations through interdisciplinary research and precision-based approaches will be essential for advancing next-generation vaccines and improving global preparedness for emerging infectious diseases.

Vaccines doi: 10.3390/vaccines14060506

Authors: Yanhong Zhao Xiaoqing Pan Fang Lv Yalu Zhu Zhen Wang Yu Lu Endong Bao

Background: Pseudorabies vaccines based on the live attenuated PRV Bartha-K61 strain remain essential for controlling pseudorabies in swine, but poor thermal stability during storage and transport limits field use. Objectives: This study aimed to develop a thermostable freeze-dried live pseudorabies vaccine through the integrated optimization of formulation and lyophilization and to preliminarily assess its humoral immunogenicity in piglets. Methods: Trehalose, mannitol, and glycine were screened as candidate lyoprotectants by single-factor experiments, followed by Box–Behnken response surface optimization using viral titer retention as the response. Critical thermal parameters were determined to establish a formulation-specific lyophilization cycle. Product quality was evaluated by post-lyophilization titer, cake appearance, residual moisture, and electron microscopy, and stability was compared with a commercial freeze-dried vaccine at 2–8 °C, 25 °C, 37 °C, and 45 °C. Conclusions: The optimized formulation, ST005, contained 9.5% trehalose, 2.0% mannitol, and 1.5% glycine. It showed a collapse-related critical temperature of approximately −34.0 °C and a dried-product glass transition temperature of 69.1 °C, produced an intact cake with residual moisture below 3.0%, and preserved viral morphology after lyophilization. Titer loss remained below 1.0 log10 TCID50/mL for 24 months at 2–8 °C, 9 months at 25 °C, 21 days at 37 °C, and 9 days at 45 °C, outperforming the commercial comparator. In PRV-seronegative piglets, stored ST005 induced robust gB-specific and neutralizing antibody responses after storage under refrigerated, ambient, and accelerated conditions.

Vaccines doi: 10.3390/vaccines14060505

Authors: Jacques L. Tamuzi Patrick D. M. C. Katoto Doris Y. Sakala Serge M. Zigabe Charles S. Wiysonge Peter S. Nyasulu

Introduction: A knowledge gap exists around which interventions can be implemented to minimise missed opportunities for vaccination (MOVs) in children under age five. Children under age five experience higher rates of MOVs, making them a critical focus for interventions to reduce MOV. This study aims to plot evidence-based interventions reducing MOVs in children under age five. Methods: We performed an electronic search without any language restriction for studies indexed between 1 January 1990 and 30 August 2025 in PubMed (Medline), Web of Science, Cochrane Central Register of Controlled Trials, Scopus, CINAHL, and other sources. We included studies highlighting interventions reducing MOVs in children under age five. A meta-analysis was conducted using the random-effects model with risk ratios (RRs) and 95% confidence intervals (CIs). When meta-analysis was not possible, results were reported individually. Results: Out of 535 papers reviewed via titles and abstracts, 21 were included in the meta-analysis. Overall, education interventions reduced the risk of MOVs by 35% (RR 0.65, 95% CI 0.47 to 0.91). Our results also showed that electronic immunisation registries (EIRs) and alerts were successful in lowering the risk of MOVs by 29% (RR 0.71, 95% CI 0.54 to 0.92). Integrated delivery of health interventions reduced the risk of MOVs by 66% (RR 0.34, 95% CI 0.14 to 0.83). Other interventions that reduced the risk of MOVs included integrating a pharmacist in the under-five vaccination programme (RR 0.43, 95% CI 0.26 to 0.72) and multicomponent interventions (RR 0.62, 95% CI 0.48 to 0.80). Financial incentives (RR 0.87, 95% CI: 0.80, 0.94) and combined vaccines (RR 0.72, 95% CI 0.68 to 0.76) showed a statistically significant MOV reduction. However, our results were graded from very low-to-moderate grade evidence. Conclusions: Education interventions, EIRs and alerts, pharmacist inclusion in vaccination programme, integrated delivery of health interventions, multicomponent interventions, combined vaccines, and financial incentives may improve MOVs in children under age five as the evidence was graded from very low to moderate.

Vaccines doi: 10.3390/vaccines14060504

Authors: Dilnaz Konbayeva Lespek Kutumbetov Balzhan Myrzakhmetova Olga Chervyakova Kuandyk Zhugunissov Askhat Myngbay Gulnar Altayeva Saida Askatkyzy Togzhan Nurdauletova Gulmira Abulgazimova Nadezhda Burambayeva Arman Issimov

Background: Mpox is a re-emerging viral zoonotic disease that remains relevant for public health preparedness, risk communication, and vaccination literacy. University students are an important population for infectious disease communication because they are socially active, digitally connected, and may act as knowledge multipliers. This study assessed Mpox-related knowledge, risk perception, preventive practices, and willingness to receive Mpox vaccination among university students in Aktobe, Kazakhstan, and identified independent predictors of adequate knowledge and vaccination willingness. Methods: A cross-sectional questionnaire-based survey was conducted among students from three universities. The questionnaire collected socio-demographic characteristics, Mpox-related knowledge, information sources, attitudes, preventive practices, perceived risk, and vaccination willingness. Knowledge was summarized using a three-item score; adequate knowledge was defined as a score of at least 2 out of 3. Two multivariable logistic regression models were fitted: one for adequate Mpox-related knowledge and one for willingness to receive Mpox vaccination. Results: The final descriptive dataset included 482 respondents. Most participants were female (66.8%), from urban areas (80.5%), and aged 17–18 years (61.6%). Only 217 students (45.0%) had previously heard about Mpox, 193 (40.0%) correctly identified rash as the main symptom, and 179 (37.1%) knew that vaccination against Mpox exists. Adequate knowledge was observed in 201 students (41.7%), while only 150 students (31.1%) were willing to receive Mpox vaccination. In the multivariable model, adequate knowledge was independently associated with studying at Marat Ospanov West Kazakhstan Medical University (aOR = 5.66; 95% CI: 2.95–10.84), use of medical websites as an information source (aOR = 1.71; 95% CI: 1.09–2.69), and following infectious disease news (aOR = 2.81; 95% CI: 1.76–4.48). Vaccination willingness was independently associated with considering Mpox a dangerous infectious disease (aOR = 2.04; 95% CI: 1.11–3.77) and perceiving Mpox as a threat to Kazakhstan (aOR = 2.16; 95% CI: 1.30–3.59). Conclusions: Mpox-related knowledge among university students in Aktobe was limited, while vaccination willingness remained low despite moderate perceived risk. Reliable information exposure improved knowledge, whereas vaccination willingness was more strongly associated with perceived disease threat. These findings support university-based health literacy, vaccine literacy, and risk communication interventions aimed at improving preparedness for emerging infectious diseases.

Vaccines doi: 10.3390/vaccines14060503

Authors: Michelle M. Gill Assucênio Chissaque Edna Viegas Lillian Chinyanganya Hilda Bara Lauren Greenberg Nontokozo Gava Mahira Amade Bridget Kanengoni Angela Mushavi Leonildo Augusto Nhampossa Aleny Couto Neiva Banze Humberto Inguane Epifânia Orlando Raimundo Patricia Pérez Martin Laura Guay Rhoderick Machekano

Background/Objectives: Girls living with HIV (GLHIV) or vulnerable to HIV have a higher risk of HPV infection and cervical cancer as they age. We determined acceptability and vaccination uptake after integrating HPV vaccination into HIV prevention and treatment services for girls in Mozambique and Zimbabwe. Methods: Pre-integration and integration HPV vaccination information were abstracted from routine records of girls aged 9–14 years offered HPV vaccine through HIV services in 54 health facilities (HFs) and surrounding communities between February and December 2025. Caregivers participated in quantitative surveys about vaccine perceptions and integration model experiences in a subset of 16 HFs. Results: In total, 6377 records of girls (median age: 11 years) were abstracted. Among the vaccine recipients, 63 (3.0%) girls received vaccine pre-integration and 2019 (97.0%) post-integration in Mozambique and 743 (17.3%) pre-integration and 3541 (82.7%) post-integration in Zimbabwe. Among GLHIV, 95.8% and 69.6% received a first HPV vaccine in Zimbabwe and Mozambique, respectively. Full vaccination with two doses occurred in 49.1% of eligible girls in Mozambique and 73.9% in Zimbabwe. Overall, 461 (67.8%) caregivers had heard of the HPV vaccine and 85.9% of cervical cancer, 99.6% were satisfied with vaccination in integration settings, and 78.6% preferred facility-based vaccination models. Conclusions: We demonstrated that HPV/HIV service integration was an effective strategy to increase HPV vaccine uptake among young girls at increased risk of HPV and cervical cancer. We found high vaccine and model acceptability and awareness of cervical cancer among caregivers. Optimization of this approach requires better integrated tools and model adaptations to fit the needs of girls and health systems.

Vaccines doi: 10.3390/vaccines14060502

Authors: Susanna Esposito Nigel Curtis Ulrich Heininger Markus Knuf Shamez Ladhani Helen Marshall Federico Martinon-Torres Marco Safadi Vana Spoulou Mohamed K. Taha Nicola Principi

Background: Invasive meningococcal disease (IMD) remains a rare but severe condition associated with high mortality and a significant risk of long-term sequelae. Despite global vaccination efforts, the epidemiology of Neisseria meningitidis continues to evolve, with serogroup B (MenB) representing the predominant cause of IMD in many high-income countries. Methods: This consensus document reviews current evidence on MenB epidemiology and the role of the multicomponent meningococcal serogroup B vaccine (4CMenB), with a focus on immunogenicity, strain coverage, real-world effectiveness, and remaining challenges. Results: Protein-based MenB vaccines have overcome the limitations of polysaccharide approaches, demonstrating robust immunogenicity across age groups. Real-world data confirm substantial vaccine effectiveness, particularly in infant immunization programs and outbreak settings, with significant reductions in disease incidence. For example, in England in the 3 years after vaccine introduction, MenB IMD incidence declined by 75% in immunized infants compared to unvaccinated controls. Adjusted vaccine efficacy was 52.7% after the two-dose primary series and 59.1% following the booster dose, highlighting the contribution of the booster. However, protection is influenced by antigenic variability among circulating strains, resulting in incomplete and geographically variable coverage. In addition, antibody waning over time and the limited impact on nasopharyngeal carriage reduce the potential for long-term and indirect protection. These factors highlight the need to optimize vaccination strategies, including the timing of booster doses, particularly in adolescents, and the role of vaccination in different epidemiological contexts. In this regard, it is not precisely defined whether infants who were immunized in the first year of life need a booster dose in the preschool period, especially in countries with a high incidence of MenB disease. Moreover, it is not established whether and when adolescents who were vaccinated both in infancy and during the preschool period need a booster dose. Economic considerations and variability in national immunization policies further contribute to heterogeneity in vaccine implementation. Emerging evidence suggests possible cross-protection against other meningococcal serogroups and Neisseria gonorrhoeae, although findings remain inconsistent across different risk groups and do not allow us to recommend 4CMenB vaccine beyond MenB IBD prevention. Conclusions: 4CMenB is an effective tool for preventing MenB IMD, although further studies are needed. Future strategies should prioritize age-targeted boosting and enhanced genomic surveillance to maximize impact.

Vaccines doi: 10.3390/vaccines14060501

Authors: Ado Mpia Bwaka Marcellin Mengouo Nimpa Rija Andriamihantanirina Alain Komi Ahawo Daman Keita Evanilda Santos Desmond Maada Kangbai Milse William Nzingou Mouhembe Yves Medessi Armand Mongbo Tene-Alima Essoh Christian Tague Criss Koba Mjumbe Akpaka Kalu Benido Impouma

Background: The 2025 EPI Managers’ Meeting for West African countries in Guinea was a critical platform for EPI managers to make an in-depth analysis of immunization programmes. We present a structured analysis of immunization status in West Africa using a WHO Health System model to move beyond descriptive reporting toward systemic analysis for actionable solutions. Methods: The meeting convened EPI managers from 14 of the 17 West African countries and partners supporting the immunization program. Country and regional presentations, immunization and surveillance data and meeting discussions were analysed through a framework identifying (1) core problems, (2) systemic barriers using WHO health systems building blocks and (3) actionable recommendations or call for action. Results: Analysis revealed stagnating immunization coverage. Recovery from COVID-19 pandemic disruptions remained limited, with persistent outbreaks of vaccine-preventable diseases (VPD). Among the five Immunization Agenda 2030 objectives assessed, only Maternal and Neonatal Tetanus (MNT) elimination was on track. Four critical challenges emerged: (1) Routine immunization stagnation with DTP3 median coverage of 76%. This was associated with challenges related to poor data quality, weak implementation of innovative vaccination strategies and donor dependency, as 88.2% of countries financed less than 50% of routine vaccine costs domestically. (2) Sub-optimal progress in Big Catch-Up (BCU) implementation in some countries, revealing poor health system resilience. (3) Inability to sustain high coverage for new vaccine introductions despite significant progress, highlighting demand and service delivery gaps. (4) Persistent VPD outbreaks with geographical expansion and the resurgence of diphtheria epidemics since 2023. Conclusions: Persistent immunization challenges in West Africa appear to reflect interconnected systemic challenges, suggesting the need for a fundamental shift toward subnational strategies, integration of immunization services within primary health care (PHC) and improved data quality. Sustainable financing of the national EPI and acceleration of local vaccine manufacturing is essential to achieve immunization sovereignty in West Africa. Country Call for Action provides strategic guidance to reverse the trend toward the Immunization Agenda 2030 targets.

Vaccines doi: 10.3390/vaccines14060500

Authors: Isidoros Kougioumtzoglou Evangelia-Georgia Kostaki George Soulis Nikos Selekos Areti-Dimitra Koulouvari Dimitrios Kouvelas Nikos Maniadakis Areti Lagiou

Background: Influenza vaccination uptake among healthcare professionals remains suboptimal despite their key role in influencing public vaccination behavior. This study investigated motivational and behavioral determinants of influenza vaccination uptake and advocacy among primary healthcare professionals in Greece. Methods: A cross-sectional study was conducted among 304 physicians and pharmacists using an anonymous online questionnaire. Vaccination uptake (2023–2024 season and annual) and motivational and advocacy constructs were assessed using the validated MoVac-flu and MovAd scales. Factor structure was evaluated using confirmatory and exploratory factor analyses. Multivariable logistic regression models were applied to identify predictors of vaccination uptake. Results: The study sample consisted of 304 healthcare professionals of whom 61.2% were physicians and 38.8% were pharmacists. More than half of the participants were female (52.6%) and aged 41–60 years (57.6%). Influenza vaccination uptake was 77.6% for the 2023–2024 season and 75.3% for annual vaccination. A two-factor structure was identified for the MoVac-flu scale (F1: Vax Self-Care, F2: Vax Awareness), whereas a four-factor structure was identified for the MovAd scale (F1: Vax Communication, F2: Vax Influence, F3: Vax Confidence, F4: Vax Choice). The overall scales demonstrated high internal consistency, while most subscales showed satisfactory to high reliability. Motivation toward influenza vaccination and vaccination advocacy were high among the participants. Vaccinated participants demonstrated higher motivation and vaccination advocacy scores compared with non-vaccinated participants. In multivariable analyses, higher scores on Vax Self-Care (aOR = 3.22, 95% CI: 2.08–4.96, p < 0.001) and Vax Communication (aOR = 1.64, 95% CI: 1.14–2.34, p = 0.007) subscales, reflecting higher motivation and vaccination advocacy, respectively, as well as male sex (aOR = 2.35, 95% CI: 1.14–4.83, p = 0.020) were associated with higher odds of annual vaccination. Higher scores on the Vax Self-Care subscale (aOR = 3.66, 95% CI: 2.33–5.77, p < 0.001) were also found to be associated with higher odds of 2023–2024 vaccination uptake, as well as living with vulnerable individuals (aOR = 2.95, 95% CI: 1.18–7.38, p = 0.020). Conclusions: Influenza vaccination uptake among primary healthcare professionals in Greece was relatively high; however, it was strongly driven by intrinsic motivational factors, particularly the perceived personal and public health benefits of vaccination. Communication-related competencies also independently contributed to vaccination behavior, highlighting the link between professional practice and personal uptake. In contrast, household-related contextual characteristics, such as cohabitation with vulnerable individuals, appeared to exert a less consistent influence on vaccination behavior. These findings suggest that interventions focusing on strengthening intrinsic motivation and communication skills may contribute to sustained improvements in both vaccination uptake and advocacy among healthcare professionals.

Vaccines doi: 10.3390/vaccines14060499

Authors: Anjali Gupta Aarti Tripathi Kirtika Jha Yogita Rawat Urvashi Bhardwaj Renu Khasa Shailendra Chauhan

West Nile Virus (WNV) belongs to the orthoflavivirus genus and is part of the Flaviviridae family, which includes the Japanese encephalitis virus, Dengue virus, Zika virus, and yellow fever virus. WNV circulates among birds and mosquitoes, posing infection risks to humans and mammals. The significant rise in WNV’s geographic spread and infection rates over the past five decades has prompted urgent public health concerns, driving the need for accelerated vaccine research. The development of a vaccine for WNV infection presents several challenges, primarily due to the virus’s complex biology, the risk of cross-reactivity with other flaviviruses, safety concerns such as antibody-dependent enhancement (ADE), and the economic and logistical hurdles in vaccine production. Despite significant research efforts, no human vaccine has been approved, although several candidates are in various stages of development. The current review offers a comprehensive summary of the latest progress and the concomitant challenges in the development of vaccines. It also discusses the role of host–pathogen interaction, host immunity, viral immune evasion, and disease pathogenesis in facilitating the advancement of vaccines.

Vaccines doi: 10.3390/vaccines14060498

Authors: Fanzhi Kong Nannan Wu Shuxuan Liang Yufeng Yan

Porcine enteric coronaviruses (PECs), including porcine epidemic diarrhea virus (PEDV), transmissible gastroenteritis virus (TGEV), porcine deltacoronavirus (PDCoV), and swine acute diarrhea syndrome coronavirus (SADS-CoV), remain major causes of neonatal diarrhea, dehydration, mortality, and economic loss in swine production. Despite substantial progress in vaccine development, durable field protection is still inconsistent. In this narrative review, this narrative review synthesizes current knowledge on PEC vaccine design from three connected perspectives: antigenic breadth, mucosal immunity, and translational evaluation. The economic and virological context of PEC vaccine development is first summarized, including the recurrent production burden of PECs, coronavirus genome organization, structural proteins, and the central role of the spike protein in receptor engagement, membrane fusion, and neutralizing antibody induction. Key issues are then discussed, including how spike diversity, conformational stability, epitope accessibility, glycan shielding, and antigen matching influence protective breadth; why intestinal secretory IgA, mucosal immune-cell trafficking, local memory responses, and lactogenic immunity should be prioritized as biologically relevant endpoints; and how delivery route, adjuvant selection, and platform design shape response quality. Current evidence on recombinant protein, viral-vectored, nanoparticle, virus-like particle, probiotic, plant-derived, and mRNA-based approaches is compared with attention to both promise and current evidentiary and translational limitations. The available literature suggests that future progress in PEC vaccinology is likely to depend less on platform novelty alone than on integrated vaccine designs that align antigen selection, mucosal delivery, maternal–neonatal protection, heterologous challenge, manufacturability, and field applicability.

Vaccines doi: 10.3390/vaccines14060497

Authors: Haider Altay Ibrahim Al-Hashimi Josh Matthews Grace DeAlessandro Ghanshyam H. Ghelani

Therapeutic cancer vaccines are a promising immunotherapy approach in genitourinary (GU) cancers, designed to stimulate antitumor immune responses through antigen-specific T-cell activation. Although agents such as bacillus Calmette–Guérin in bladder cancer and sipuleucel-T in prostate cancer have shown success, vaccine monotherapy has generally produced limited clinical benefit due to tumor heterogeneity, poor immune infiltration, and immunosuppressive tumor microenvironments. Multiple vaccine platforms have demonstrated safety and immunogenicity in prostate, renal cell, and urothelial cancers, but efficacy remains modest. Current strategies focus on multi-antigen targeting, improved antigen presentation, and combination therapies with immune checkpoint inhibitors, radiotherapy, and targeted agents to enhance antitumor activity. Advances in personalized vaccine design and delivery systems are driving progress, though challenges such as manufacturing complexity, cost, and biomarker development remain. Ongoing translational and clinical research will be critical to improving the effectiveness of vaccine-based immunotherapy in GU malignancies.

Vaccines doi: 10.3390/vaccines14060496

Authors: Amina Al-Jardani Najma Al-Kharusi Mohamed Al-Bulushi Adil Al-Wahaibi Neima Al-Shekaili Suad Al-Fahdi Rajesh Kumar Seif Al-Abri Azza Al-Rashdi

Background/Objectives: Following the introduction of the 13-valent pneumococcal conjugate vaccine (PCV13) in Oman, this study aimed to characterize the genomic epidemiology, serotype distribution, and antimicrobial resistance (AMR) of Streptococcus pneumoniae causing invasive pneumococcal disease (IPD). Methods: All IPD isolates collected through national laboratory-based surveillance between 2018 and 2021 were analyzed using Whole-Genome Sequencing (WGS). Bioinformatics tools determined serotypes, multilocus sequence types (MLSTs), and Global Pneumococcal Sequence Clusters (GPSCs). Clinical correlates and predictors of mortality were assessed via multivariate logistic regression. Results: A total of 129 IPD isolates were included. Serotype 3 (11.6%) was the most prevalent, followed by 23B and 9N (10.8% each), and 8 (8.5%). PCV13 serotypes accounted for only 26.4% of isolates, while PCV20 coverage reached 59.7%. Significant clonal diversity was observed, with GPSC12 (Serotype 3) and GPSC699 (Serotype 9N/13) being prominent lineages. Multidrug resistance (MDR) was identified in 36.4% of isolates, primarily driven by GPSC6 and GPSC699. The case fatality rate was 23.0%. Advanced age (≥65 years) and clinical presentation with bacteremia were significant independent predictors of death, whereas bacterial genotype and AMR status were not. Conclusions: The findings demonstrate significant serotype replacement in Oman after the introduction of PCV13. The high prevalence of non-vaccine serotypes and emerging MDR clones justifies the transition to higher-valency vaccines like PCV20. Sustained genomic surveillance remains essential to monitor the evolving landscape of invasive pneumococcal lineages.

Vaccines doi: 10.3390/vaccines14060495

Authors: Stephen Wiblin Mohana Kunasekaran Raina MacIntyre Holly Seale

Objective: To identify demographic, clinical, and behavioural determinants of COVID-19 vaccination and antiviral uptake in Australia using the Capability, Opportunity, Motivation-Behaviour (COM-B) framework with psychometric validation and LASSO-enhanced variable selection. Methods: Cross-sectional analysis of the 2024 KAB BREATHE survey (n = 5177) of Australian adults, intentionally enriched for risk-stacked (more than 1 chronic condition). Primary outcomes included 2023/2024 COVID-19 booster receipt, future vaccine intentions, vaccine/antiviral beliefs and antiviral uptake. Predictors included demographics, chronic conditions, and domain-specific leave-one-out (LOO) COM-B scores standardised to mean = 0, SD = 1. COM-B domains were assessed using Cronbach’s alpha. Univariate and multivariable logistic regression models were complemented by LASSO penalised logistic regression with 10-fold cross-validation. Results: Among 5177 Australian adults, the mean age was 51.5 years (SD 16.5), 61.4% (3179/5177) were female, and 70.3% (3638/5177) were classified as risk-stacked. Booster uptake declined sharply from 50.8% (2023) to 19.1% (2024). Cronbach’s alpha showed poor internal consistency for Capability (α = 0.006) and Opportunity (α = −0.383) but was acceptable for full Motivation (α = 0.78). In adjusted models, age (aOR 1.02–1.03 per year), medically associated risk factors (aOR 1.66–3.51), and tertiary education (aOR 1.34–1.79) consistently predicted higher uptake and intention. Renting (aOR 0.59–0.78) and current employment (likely inversely associated with age) (aOR 0.73–0.83) were associated with lower uptake across all vaccine outcomes. Adding LOO COM-B scores substantially improved model fit (e.g., 2024 booster AUC 0.73→0.83); Motivation per SD was the strongest predictor (aOR 2.44–4.94 for vaccine outcomes, 1.52–2.49 for antivirals). LASSO models achieved CV-AUCs of 0.78–0.87. Among COVID-positive respondents (n = 2576), only 15.2% received antiviral treatment. Conclusions: Age, clinical risk, and socioeconomic factors, particularly housing tenure and employment status, are key drivers of COVID-19 preventive behaviours (either positively or negatively). The COM-B framework, when corrected for circular prediction and validated via Cronbach’s alpha and LASSO, provides substantial explanatory value. Targeted interventions should address structural barriers faced by renters and younger, employed individuals while leveraging high motivation among older adults and clinically vulnerable groups. Implications for Public Health: These findings support a shift from knowledge-based campaigns towards equity-focused, multi-level public health strategies that address structural barriers to COVID-19 vaccination and antiviral access in Australia.

Vaccines doi: 10.3390/vaccines14060494

Authors: Tatiana Kotomina Pei Fong Wong Victoria Matyushenko Nikolay Zaramenskikh Maria Bolgar Anna Bazhina Ekaterina Stepanova Larisa Rudenko Irina Isakova-Sivak

Background/Objectives: Respiratory syncytial virus (RSV), human metapneumovirus (hMPV), and parainfluenza virus type 3 (PIV3) are leading causes of acute respiratory infections in children and the elderly, yet no licensed T-cell vaccines are available. This study aimed to develop multivalent T-cell vaccine candidates against these pathogens using a live attenuated influenza virus (LAIV) vector platform. Methods: Conserved F, N, and M proteins of RSV, hMPV, and PIV3 were identified through multiple sequence alignments. Fragments enriched with experimentally confirmed and predicted T-cell epitopes were selected using the IEDB and NetMHCpan servers. These fragments were assembled into polyepitope immunogenic cassettes, and their selected order was determined by thermodynamic analysis of mRNA secondary structures using the RNAfold Web Server. The selected cassettes were cloned into the neuraminidase (NA) gene of a cold-adapted LAIV vector. Recombinant viruses were rescued by reverse genetics and assessed for replicative fitness in embryonated chicken eggs and MDCK cells, NA enzymatic activity and genetic stability upon serial passaging. Results: Four cassettes were designed for RSV, three for hMPV, and one for PIV3, all containing fragments with multiple T-cell epitopes. Three recombinant viruses of LAIV/RSV type and three of LAIV/hMPV type were successfully rescued, while attempts to recover the remaining recombinant viruses, i.e., LAIV/RSV and LAIV/PIV3, were not successful. All rescued recombinant viruses replicated to titers comparable to the parental LAIV strain and retained the full-length insert for at least eight passages in eggs. Importantly, NA enzymatic activity of the LAIV vector was not compromised by the insertion of the polyepitope T-cell cassettes. Conclusions: We developed a panel of recombinant T cell-based vaccine candidates against RSV and hMPV using the LAIV vector platform. These recombinant viruses encode conserved T-cell epitopes of the target viruses while retaining the biological properties of LAIV strains. Taken together, these characteristics warrant further evaluation of these recombinant viruses in appropriate relevant in vitro models to directly assess their immunogenicity in terms of stimulating a T-cell response against target pathogens.

Vaccines doi: 10.3390/vaccines14060493

Authors: Albert Judith Muruganantham Lillimary Eniya Beulah Faith Poongulali Selvamuthu Ramamurthy Silamban Yazhini Nagalingeswaran Kumarasamy Stephen J. Challacombe Priya Kannian

Background/Objectives: The induction of anti-SARS-CoV-2 antibodies by COVID-19 vaccination reduces morbidity and mortality, but immune responses may be compromised in people living with HIV (PLWH). The aims of the current study were to determine whether viral suppression (VS) or immune reconstitution (IR) in PLWH directly affected their ability to produce effective levels of anti-SARS-CoV-2 antibodies in mucosal secretions or blood induced by vaccination. Methods: Anti-SARS-CoV-2 spike IgG, IgA and secretory IgA (SIgA) antibodies and their avidities were measured by ELISA in HIV-negative healthy controls (HC; n = 49) and PLWH (n = 94) using stimulated oral fluid (SOF) and serum. Frequencies of CD4/CD8 T cells and their expression of exhaustion/senescence were determined by flow cytometry. Cytokine levels were measured by cytokine bead arrays. Results: We showed that higher HIV burden negatively impacted the levels of systemic and mucosal anti-SARS-CoV-2 spike IgG antibodies produced. This differential IgG antibody production was unaffected by IR status, antiretroviral therapy duration or T cell exhaustion/senescence. PLWH elicited higher anti-SARS-CoV-2 spike IgA antibodies both in peripheral blood and oral mucosa and highr secretory IgA (SIgA) antibodies in the oral mucosa. PLWH with higher HIV RNA copies elicited lower IgG avidity but the IgA avidity indices remained unaffected. PLWH expressed higher levels of innate immunity cytokines in the oral mucosa, irrespective of the HIV RNA copies. Conclusions: Significantly fewer breakthrough infections in PLWH compared with HC, along with high IgA/SIgA antibodies and increased innate immunity cytokines in the SOF, suggest a potential role for mucosal immunity in the immunopathogenesis of COVID-19.

Vaccines doi: 10.3390/vaccines14060492

Authors: Peter Goldstein Tania Gensale Shannon Harris Tina M. Green Stephanie Noviello Keith Rubin Camille Locht Breeze Cavell Andrew Gorringe Luc Gagnon

Background/Objectives: Pertussis, caused by Bordetella pertussis, remains a global health problem, despite high vaccine coverage. In countries with high acellular pertussis vaccine (aPV) coverage, pertactin-negative B. pertussis strains emerged due to vaccine pressure on the sole bactericidal target of aPVs. In contrast, the live attenuated intranasal vaccine BPZE1 induces bactericidal antibodies to multiple antigenic targets that kill pertactin-positive and pertactin-negative B. pertussis strains. Here, we developed two high-throughput human complement-mediated serum bactericidal assays (SBA) using clinical samples to demonstrate bactericidal activity against B. pertussis. Methods: Assay accuracy, precision, linearity, range and robustness of the SBAs against pertactin-positive and pertactin-negative B. pertussis strain B1917 were determined using a panel of commercial and clinical trial samples. The assay was used to analyze a cohort of BPZE1 and tetanus–diphtheria–acellular pertussis (Tdap) vaccinee samples at baseline and 28 days post-vaccination from a phase 2b clinical trial. Results: Inter- and intra-assay variability of both assays had coefficients of variation for repeatability < 20% and for intermediate precision of <30%. The assays measured titers ranging from ~8 to ~20,000 and showed high linearity (R2 > 0.98) between bactericidal titers and serum dilutions. On clinical samples, BPZE1 induced similar bactericidal activity as Tdap against pertactin-positive B. pertussis, despite inducing lower anti-aP antigen IgG concentrations than Tdap. Additionally, BPZE1 induced serum bactericidal activity against pertactin-negative B. pertussis, while Tdap did not. Conclusions: High-throughput SBAs were developed and qualified against pertactin-positive and pertactin-negative B. pertussis, enabling measurement of 120 samples per day per analyst. These assays will support clinical development of next-generation pertussis vaccines, including BPZE1.

Vaccines doi: 10.3390/vaccines14060491

Authors: Yuqi Fu Yuan Dang Yuming Liu Yangmu Huang

Background: Short-form video platforms have become important channels for vaccine science communication, yet whether professionally produced vaccine content aligns with audience demand remains underexplored. Methods: We conducted a cross-sectional quantitative content analysis of 3752 publicly available vaccine-related videos retrieved from three major Chinese short-form video platforms between 21 November and 13 December 2024. A coding framework based on the Health Belief Model (HBM) and the World Health Organization (WHO) Behavioral and Social Drivers (BeSD) framework was used to identify key content themes. Multivariate Bayesian negative binomial regression and demand–avoidance analysis were used to examine engagement patterns and supply–demand alignment across account types. Results: Individual users produced the majority of videos (53.17%), whereas medical professionals received the highest level of engagement. Engagement was positively associated with themes related to disease severity (β ≈ 0.19–0.25) and side effects and management (β ≈ 0.31–0.67), but negatively associated with vaccine effectiveness (β ≈ −0.28 to −0.14) and vaccination precautions (β ≈ −0.28 to −0.27). Professional sources showed broader thematic coverage but also the greatest supply–demand mismatch, with mismatch indices of 0.377 for medical institution official media and 0.304 for medical professionals, primarily driven by overrepresentation of themes associated with audience avoidance. Conclusions: Significant structural mismatch exists between professionally produced vaccine content and audience engagement-based demand on short-form video platforms. Optimizing vaccine communication may require prioritizing audience-concerned risk-related information and dynamically adjusting content strategies based on engagement feedback to enhance the effectiveness of vaccine education.

Vaccines doi: 10.3390/vaccines14060490

Authors: Joseph Magoola Brooke N. Aksnes Immaculate Ampeire Yvette Wibabara Ciara E. Sugerman Kirsten Ward

Background: In Uganda, COVID-19-related disruptions increased the number of children who missed scheduled routine vaccination (defaulters). Identifying and following up with defaulter children is important for improving vaccination coverage. This paper describes Uganda’s experience in revitalizing community-led defaulter tracking to improve vaccination coverage post-COVID-19 in four purposefully selected districts. Methods: During two 6-month periods in 2022 and 2024, healthcare workers (HCWs) worked with village health teams (VHTs) to review health facility-based immunization registers, identify and track defaulters aged 0 to 59 months. VHTs visited identified defaulters’ homes, reviewed vaccination histories and reminded caregivers to bring defaulters to immunization sites for catch-up vaccination. Results: Overall, 20,922 defaulters were identified by health register review; VHTs located 15,749 (75.3%) through household visits, of whom 3688 (23.4%) were verified as previously vaccinated based on their home-based vaccination records, leaving 12,061 as true defaulters. Among the true defaulters, 9662 (80.1%) received at least one catch-up vaccination after follow-up by the VHT. The most frequently administered catch-up vaccines were measles–rubella first dose (MR1) at 55.4%, followed by diphtheria–tetanus–pertussis third dose (DTP3) at 48.3% and Bacillus Calmette–Guérin (BCG) at 47.4%. Among the 2399 children who remained unvaccinated after follow-up, the most common reasons were relocation outside the original catchment area (49.5%) and caregiver intention to vaccinate later (16.3%). Conclusion: Community-led defaulter tracking was feasible and improved vaccination uptake in post-COVID-19 Uganda. Strengthening the quality and availability of health facility immunization data, along with targeted community engagement, caregiver reminders and integrated vaccination services would improve identification and follow-up of defaulters, reducing population immunity gaps.

Vaccines doi: 10.3390/vaccines14060489

Authors: Siyang Chan Dachuang Zhou Di Zhang Yuting Xia Wenxi Tang

Background/Objectives: Vaccine clinical trials face high costs, long timelines, and variable progression rates, yet systematic evidence linking trial design features to progression outcomes remains limited. This study aimed to identify trial design features associated with vaccine trial progression and to explore robust design configurations using machine learning approaches. Methods: We analyzed 1618 vaccine trials registered from 2012 to 2022. Progression was defined as phase advancement (phase I/II) or regulatory authorization (phase III). Logistic regression assessed associations with progression. Random forest classifiers with cross-validation were used to estimate predicted progression probabilities based on combinations of design features. Monte Carlo simulations compared model-identified robust configurations with randomly generated configurations. Results: Among 1618 trials, 579 achieved phase progressions, corresponding to an overall observed progression rate of 35.8%. Larger sample size, preventive vaccine purpose, COVID-19 indication, and enrollment across all age groups were consistently associated with higher observed odds of progression in both univariable and multivariable logistic regression analyses. In machine learning analyses, the pooled mean predicted progression probability of model-identified robust configurations was 48.93%, compared with 39.44% for historically observed design configurations, corresponding to a relative increase of 24.1%. Simulations further showed a lower projected cumulative development duration (106.87 vs. 128.25 months; −16.7%) and reduced projected cost (USD 100.67M vs. USD 108.33M; −7.1%) for robust configurations compared with historical strategies. Conclusions: This study provides a data-driven framework for characterizing historical vaccine trial design patterns. By integrating machine learning with observational registry data, it supports hypothesis generation and descriptive benchmarking of design features that may inform the design of future prospective or causal investigations.

Vaccines doi: 10.3390/vaccines14060488

Authors: Carlos Espinal Tejada Marisa Aizenberg Zulma Cucunubá Wilfrido Coronell Rodríguez Judit Díaz Bazán Fernando Ariel García Terrón Gamaliel Gutiérrez Alejandro Llanos Cuentas Martín Casapia Morales José Guadalupe Martínez Núñez José Alejandro Mojica Tomás Orduna Victoria Pando Robles Mariana Rico-Restrepo Jaime R. Torres Mauricio Javier Vera Soto Iván Darío Vélez

In March 2025, the Americas Health Foundation (AHF) convened a regional meeting, in Bogotá, Colombia, of the Latin America Dengue Task Force, a multidisciplinary regional group of arbovirus specialists, to address the growing challenges posed by dengue in the region. The primary objective of the meeting was to analyze the regional dengue landscape, identify gaps and barriers that hinder a comprehensive approach, and develop a strategic blueprint for advancing control and prevention in Latin America. The Task Force conducted a thorough review of dengue-related issues, drawing on participants’ professional expertise in vaccination, prevention, diagnosis, treatment, vector control, environmental determinants, and regulatory and policy frameworks. Key barriers identified include underreporting, widespread insecticide resistance, structural weaknesses in the health system, fragmented surveillance, financial and political constraints, and socioeconomic drivers. Based on these findings, actionable recommendations were developed to optimize regional dengue surveillance, strengthen prevention and diagnosis strategies, and improve coordination among stakeholders. This narrative review summarizes the epidemiological context, presents expert guidance to overcome existing limitations, and outlines strategies to advance integrated dengue control in Latin America.

Vaccines doi: 10.3390/vaccines14060487

Authors: Hye-Young Jang Young Ko Song Yi Han

Background/Objectives: Healthcare workers play a critical role in vaccination programs, yet vaccine hesitancy has been widely reported even among this group during the Coronavirus disease 2019 (COVID-19) pandemic. Previous studies have primarily focused on identifying factors associated with vaccine acceptance, offering limited insight into the processes underlying decision-making. This study aimed to synthesize qualitative studies on healthcare workers’ COVID-19 vaccination experiences to develop a comprehensive understanding of their decision-making processes. Methods: A qualitative meta-synthesis was conducted using the thematic synthesis approach proposed by Thomas and Harden. Electronic databases including PubMed, Embase, and CINAHL were searched for qualitative studies published up to February 2026. Thirteen studies were included following PRISMA guidelines. Data were analyzed through line-by-line coding, followed by the development of descriptive and analytical themes. Results: Four analytical themes were identified: (1) vaccination as a dynamic risk–benefit negotiation process, (2) trust as a central mechanism shaping information interpretation, (3) socially embedded and relationally negotiated decision-making, and (4) moral identity as a driver of vaccination behavior. Healthcare workers’ vaccination decision-making was not a static choice but an evolving process shaped by continuous appraisal of risks and benefits, filtered through trust in information and institutions, influenced by social interactions, and guided by professional identity and ethical responsibility. Conclusions: Healthcare workers’ vaccination decision-making is a multidimensional process embedded in cognitive, social, and ethical contexts. Interventions should move beyond individual-level approaches and instead focus on building trust, leveraging social networks, and reinforcing professional identity with implications for future public health crises.

Vaccines doi: 10.3390/vaccines14060486

Authors: Deena N. Brosi Gregory Tung Beth M. McManus Srinivas Parinandi Glen P. Mays

Background/Objectives: COVID-19 vaccine resistance was detrimental to herd immunity and worsened COVID-19 morbidity and mortality during outbreaks. Despite more evidence showing reactionary behavior among residents exposed to vaccine mandates, little research has been conducted on the effects of state proof-of-vaccine (POV) mandate bans in the United States (US). We sought to investigate the causal effects of POV mandate bans, overall and stratified by policy passage via executive order or state legislature, on first-dose COVID-19 vaccinations. Methods: In the contiguous US, 21 states enacted POV mandate bans from 8 February 2021–25 October 2021. Using a geographic regression discontinuity design, we selected treatment and control counties within 150 miles of the POV mandate ban state border. The resulting sample was 4612 county-observations and 2466 unique counties. We conducted two-way fixed-effects estimation to compare changes in weekly, first-dose COVID-19 vaccinations among individuals <65 years old before and after POV mandate ban enactment between treatment and control counties. Results: Among executive order POV mandate ban counties, we saw an additional increase in weekly, first-dose COVID-19 vaccinations following POV mandate ban enactment when compared to controls. There was an additional 38.2% increase in Weeks 1–2, 40.6% in Weeks 3–4, 41.3% in Weeks 5–6, and 43.9% in Weeks 7–8. Conclusions: While seemingly counterintuitive, these findings follow Psychological Reactance Theory. Once the perceived threat to freedom was removed, reactance to COVID-19 vaccinations declined and constituents received the COVID-19 vaccine of their own volition. Future public health efforts should consider potential reactance to mandatory policies and tailor efforts to community values.

Vaccines doi: 10.3390/vaccines14060485

Authors: Rosa Katia Bellomo Maria Assunta Donato Vito Cerabona Teresa Esposito Alessia Perna Giuliana Federico Carmine Guarino Anna Odone Michele Sparano Romina Sezzatini Erika Alessandra Strangi Eleonora Tassone Paolo Villari Corrado De Vito

Background: Epidemiological alerts about the possible spread of different pathogens have highlighted the risk of international travelers contracting infectious diseases when visiting endemic areas. The role of travelers in disease transmission underscores the importance of pre-travel consultations, which provide critical information on health risks, vaccinations, and preventive measures. Understanding travelers’ risk perceptions and behaviors is essential for enhancing global health security in the post-pandemic era. Methods: A cross-sectional study (June 2023–January 2024) was conducted by administering an anonymous questionnaire at the Rome-Fiumicino Airport International Prophylaxis Clinic (USMAF-SASN). The questionnaire explored demographics, travel patterns, risk perceptions, vaccination behaviors, and sources of health information. Descriptive statistics and a multivariable logistic regression analysis were performed to identify low-risk perception predictors. Results: Among 217 participants, 89.8% were Italian, with a balanced representation of genders. The primary purpose of travel was tourism (61.6%), followed by work-related trip (23.1%). While 77.1% rated preventive measures as effective, 23.2% evaluated infection risk as low. Being male (aOR 3.63, 95% CI 1.37–9.61), and being a hotel user (aOR 6.27, 95% CI 2.43–16.15), was significantly associated with a lower risk perception. As expected, healthcare professionals and individuals using institutional healthcare sources showed a higher risk awareness. Vaccination uptake at the Airport Clinic was motivated by self-protection, vaccine confidence, and poor time flexibility to access local vaccination services, and last-minute plans, making the airport a more convenient option. Conclusions: Travelers’ risk perception is influenced by gender, profession, accommodation type, and information sources. Public health strategies should enhance health literacy, promote pre-travel consultations, and improve access to preventive services. Strengthening collaborations between health authorities, educational institutions, and the travel sector is key to mitigating health risks and ensuring global health security. Future interventions should address structural vaccination barriers and improve outreach to under-informed travelers.

Vaccines doi: 10.3390/vaccines14060484

Authors: Binjie Wu Yuhan Sun Yang Wang Ye Wang Yuyang Han Yuan Wang Wei Ye

Background: Rift Valley fever virus (RVFV) is a mosquito-borne zoonotic pathogen that has caused repeated epidemics across Africa and the Arabian Peninsula, posing a severe and growing threat to public health and livestock. Infection in ruminants causes high neonatal mortality and catastrophic abortion storms; human disease ranges from self-limiting febrile illness to hemorrhagic fever, encephalitis, and permanent blindness. No licensed human vaccines or specific antiviral therapeutics are available, creating an urgent unmet medical need. Methods: We systematically reviewed the peer-reviewed literature on RVFV neutralizing antibodies (NAbs), extracting and synthesizing data on antibody sources, epitope specificity, in vitro neutralizing potency, in vivo protective efficacy, and molecular mechanisms of action. Results: A growing body of work has identified potent NAbs from immunized rodents, rabbits, alpacas, non-human primates, and convalescent patients. These NAbs predominantly target the Gn and Gc envelope glycoproteins. Their mechanisms include blocking host receptor (LRP1) binding, preventing the pH-dependent conformational rearrangement of the Gn–Gc complex, and directly inhibiting viral membrane fusion. Lead candidates, such as RVFV-268 and RVFV-140, achieve sub-nanogram neutralization and confer robust protection in rodent models against lethal challenge, aerosol exposure, and vertical transmission. Bispecific antibodies and combination strategies further enhance potency and the genetic barrier to viral escape. Conclusions: Substantial progress has illuminated the epitope landscape and neutralization mechanisms of RVFV, yielding promising clinical candidates. Translational challenges remain, including viral immune escape, antibody thermostability, and the need for rigorous preclinical evaluation. Future efforts should prioritize structure-guided engineering, rational antibody combinations, and testing in clinically predictive animal models.

Vaccines doi: 10.3390/vaccines14060483

Authors: Stela Stojisavljevic Mirza Palo Faris Dizdar

Background: Vaccination coverage declined in many countries during the COVID-19 pandemic, including in Bosnia and Herzegovina. We evaluated a telephone-based outreach intervention implemented in primary healthcare facilities (PHCs) in the Federation of Bosnia and Herzegovina. The intervention targeted missed routine vaccinations among children aged 0–7 years. Method: Using a programmatic, non-randomized pre–post design, healthcare teams reviewed registries to identify under-vaccinated children, and parents were contacted by phone to facilitate catch-up visits. Results: Among age-eligible children, vaccination coverage increased from 66.5% to 74.2% for measles–mumps–rubella (MMR) dose 1, from 43.4% to 51.7% for MMR dose 2, and from 50.4% to 55.9% for the fourth dose of diphtheria–tetanus–acellular pertussis-inactivated poliovirus–Haemophilus influenzae type b vaccine (DTaP-IPV-Hib). Mixed-effects models adjusting for age, sex, and clustering by facility and canton showed higher odds of vaccination post-intervention for MMR dose 1 (adjusted odds ratio [aOR] 1.65), MMR dose 2 (aOR 1.61), and DTaP-IPV-Hib dose 4 (aOR 1.39; all p < 0.001). Conclusions: These results show that registry-based, proactive outreach can yield significant improvements in routine childhood vaccination coverage in real-world settings and may be a scalable approach for decentralized health systems recovering from pandemic disruptions.

Vaccines doi: 10.3390/vaccines14060482

Authors: María Ángeles Onieva-García Irene Rivero-Calle Ángel Gil de Miguel Antoni Trilla Alberto Pérez-Rubio

Influenza is an acute viral respiratory infection that generates a substantial clinical and socioeconomic burden, especially among high-risk populations such as older adults. In Spain, influenza accounts for approximately €128 million in direct healthcare costs each season, with 80% of expenditures concentrated in individuals over 45 years of age. Vaccination remains the most effective intervention to prevent complications and reduce healthcare pressure. However, current coverage rates are consistently below international targets and continue to decline. In this context, there is an urgent need to strengthen vaccination uptake, especially among high-risk groups. Increasing vaccination uptake is essential to lessen the clinical, societal, and economic burden of influenza, since modest improvements in coverage have a significant impact on public health outcomes and economic resilience. In fact, previously published modeling analyses indicate that a 1% reduction in national vaccination coverage could result in over 6400 additional influenza cases and an additional economic burden of €1.54 million per season. Furthermore, increasing coverage to 75% in Spain could prevent approximately 180,300 additional cases—equivalent to 20% of the total—which would translate into potential savings of €43 million (€26 million in direct medical costs and €17 million in work absenteeism costs). This manuscript provides an overview of the influenza burden and vaccination landscape in Spain, focusing on clinical, societal, and economic implications of suboptimal coverage, as well as the current challenges and opportunities to improve uptake. Available evidence indicates that influenza vaccination reduces severe outcomes and healthcare burden, suggesting that mildly improving coverage in Spain could yield substantial health and economic benefits. Taken together, these findings support influenza vaccination as a public health priority and a relevant investment for health systems.

Vaccines doi: 10.3390/vaccines14060481

Authors: Kriengkrai Prasert Sutthichai Nakphook Jiraphut Kittiwatanachod Kanlaya Sornwong Suriya Naosri Passakorn Ongarj Isariya Techatanawat Piengthong Narakorn Somchaiya Surichan Jorge Flores Laina D. Mercer Christina S. Polyak Bruce L. Innis Rama Raghunandan Chakrarat Pittayawonganon Sopon Iamsirithaworn Supakit Sirilak Ponthip Wirachwong Prabda Praphasiri

Background/Objectives: HXP-GPOVac is a locally produced, inactivated Newcastle disease virus-based (NDV-HXP-S) COVID-19 vaccine manufactured in Thailand. This phase II trial compared its safety and immunogenicity with the mRNA vaccine BNT162b2 in adults aged 18–75 years. Methods: In this randomized, double-blind, active-controlled trial registered with the Thai Clinical Trials Registry (TCTR20220819003), 300 participants were assigned 3:1 to receive HXP-GPOVac or BNT162b2 on Days 1 and 29. Solicited adverse events (AEs) were recorded for 7 days after each dose, AEs were summarized through 28 days after each dose, and serious adverse events (SAEs), medically attended AEs (MAAEs), and adverse events of special interest (AESIs) were collected through Day 197. Humoral immunogenicity was assessed by pseudovirus 50% neutralization titers (NT50) and anti-spike IgG concentrations at baseline, Day 29, Day 43, and Day 197. Seroconversion was defined as a ≥4-fold increase from baseline. A predefined subset underwent interferon-γ (IFN-γ) and interleukin-5 (IL-5) ELISpot assays to assess cell-mediated immune responses. The primary immunogenicity analysis assessed non-inferiority of HXP-GPOVac compared with BNT162b2 based on the NT50 geometric mean titer ratio, with a prespecified non-inferiority margin of 0.5. Results: Solicited AEs were predominantly mild and occurred more frequently after the first dose in both groups; one or more solicited local or systemic AEs were reported by 23.7% (95% CI: 18.3–29.8) of HXP-GPOVac recipients and 44.7% (95% CI: 33.3–56.6) of BNT162b2 recipients after the first dose. AEs through 28 days after vaccination and SAEs were uncommon; MAAEs occurred in 17.0% of HXP-GPOVac recipients and 22.4% of BNT162b2 recipients, and none were considered related to vaccination. In the HXP-GPOVac group, NT50 geometric mean titers increased from 5.6 at baseline to 65.5 at Day 29 and 505 at Day 43, declining to 63.6 at Day 197. Anti-spike IgG geometric mean concentrations rose from 7.5 BAU/mL at baseline to 102.7 BAU/mL at Day 29 and 514.6 BAU/mL at Day 43, decreasing to 61.0 BAU/mL at Day 197. BNT162b2 induced higher antibody levels at all time points. The NT50 GMT ratio (HXP-GPOVac/BNT162b2) at Day 43 was 0.51 (95% CI: 0.39–0.67); the lower bound did not exceed the prespecified non-inferiority margin of 0.5, and non-inferiority was not established. Seroconversion rates at Day 43 were 97.6% for HXP-GPOVac and 97.1% for BNT162b2 (neutralizing antibody) and 98.6% and 97.1%, respectively (anti-spike IgG). ELISpot analyses demonstrated increased IFN-γ responses after the second dose without evidence of Th2-dominant skewing. Conclusions: HXP-GPOVac was well tolerated and induced substantial humoral and cellular immune responses, with high seroconversion rates and balanced T-cell polarization. Although absolute antibody levels were lower than those induced by BNT162b2 and the prespecified non-inferiority criterion was not met, these findings support continued evaluation of the inactivated NDV-HXP-S vaccine platform.

Vaccines doi: 10.3390/vaccines14060480

Authors: Julia Hutter M. Patricia D’Souza Janet M. McNicholl James R. Lane Robert W. Eisinger Cesar Boggiano

This perspective outlines the ongoing necessity for an HIV vaccine and immune-based prevention strategies in an era of availability of multiple behavioral and pharmacological HIV prevention interventions, including safe and highly effective pre-exposure prophylaxis (PrEP). We describe the approach of the National Institute of Allergy and Infectious Diseases (NIAID), Division of AIDS (DAIDS), based on key scientific progress, critical steps, and persistent challenges in achieving broad and durable immune protection against HIV. We highlight DAIDS coordinated infrastructure, clinical trial networks, and partnerships that enable iterative development and de-risk innovation for these interventions. Finally, we consider implications for trial design and priorities for advancing scalable HIV immune-based prevention.

Vaccines doi: 10.3390/vaccines14060479

Authors: Yanli Liu John M. Hickey Geetha Satya Sainaga Jyothi Vaskuri Brandy Dotson Sangeeta B. Joshi David B. Volkin

Background/Objectives: Recombinant poliovirus (PV) virus-like particle (VLP) antigens mimic the conformation of the surface proteins in native PVs (i.e., serotype-specific D-antigen epitopes). Since they lack genomes and are non-infectious, PV-VLPs offer the promise of a safer, next-generation polio vaccine compared to traditional inactivated (IPV) or attenuated live (OPV) vaccines. Sandwich D-antigen ELISA formats are commonly used to measure the in vitro potency values (relative D-antigen content, DU/mL) of unadjuvanted trivalent IPV antigens. If IPV is formulated with aluminum-salt adjuvants, however, a pretreatment step (i.e., adjuvant dissolution or antigen desorption) is required, which may compromise antigen integrity during sample handling. Methods: This work describes the development of three competitive ELISAs to measure the relative D-antigen content of aluminum-salt adjuvanted PV-VLPs (Types 1, 2, 3) without the need for pretreatment. Results: First, key assay parameters were established, including specificity, accuracy, precision, linearity, limit of quantification, and stability-indication. Next, preformulation characterization studies were performed with these methods including (1) rank-ordering the inherent thermal stability profiles of the PV-VLPs (Types 1 > 3 > 2) in-solution and adsorbed to an aluminum phosphate adjuvant (AdjuPhos™, AP) and (2) determining the effect of formulation variables on the thermal stability profiles of AP-adsorbed PV-VLPs including antimicrobial preservatives (thimerosal, 2-PE) and five different antigens present in pediatric combination vaccines (D, T, wP, Hib, Hep B). Conclusions: The development and application of three competitive D-antigen ELISAs were demonstrated, and future use in formulation and storage stability studies with the AP-adjuvanted, trivalent PV-VLPs (Types 1, 2, 3) is discussed with the long-term goal to develop a stable, efficacious, multi-dose, hexavalent combination vaccine presentation.

Vaccines doi: 10.3390/vaccines14060478

Authors: Irina Profir Cristina-Mihaela Popescu Alexandru Nechifor Mădălin Guliciuc Ada Stefanescu

Background: Influenza vaccination coverage among children remains critically low in Romania, yet regional data contextualizing the clinical burden relative to local vaccine uptake are scarce. Methods: A retrospective descriptive study was conducted at “Sf. Ioan” Clinical Emergency Pediatric Hospital in Galați, Romania, including all patients aged 0–14 years with Reverse Transcriptase Polymerase Chain Reaction (RT-PCR)-confirmed influenza over six consecutive seasons (October 2019–April 2025). Regional influenza vaccination coverage data for children aged 0–14 years and pregnant women were obtained from county public health authority records and contextualized against Romanian National Institute of Statistics population data. Results: A total of 525 unvaccinated children were included. The median age was 2 years (IQR 1–5); 50.5% were aged 2 years or younger. Multisystem clinical involvement was documented in 97.52% of patients, with respiratory involvement predominating (86.66%). The median length of hospital stay was 5 days (IQR 4–7). Regional vaccination coverage never exceeded 2.0% of the eligible pediatric population in any study year, falling to 0.3% in 2023 and 0.1% in 2025. Infants aged 0–2 years were consistently the least vaccinated group (0–5 months not eligible for vaccination). Maternal vaccination was effectively absent in most seasons. Conclusions: These findings document a critical and persistent influenza vaccination gap among children and pregnant women in Galați County. Targeted public health interventions to improve vaccine uptake—particularly for infants, young children, and pregnant women—are urgently needed in this and similar low-coverage Eastern European settings.

Vaccines doi: 10.3390/vaccines14060477

Authors: Luka Dragačević Veljko Blagojević Marko Vasić Rajna Minić Ivana Ćuruvija Ivana Prijić Raisa Petrović Darko Rogić Irena Živković

Background: The Global Action Plan for Influenza Vaccines, launched by the World Health Organization in 2006, aimed to expand global manufacturing capacity, ensure equitable access to influenza vaccines, and reduce global vaccine shortages. The Institute of Virology, Vaccines and Sera “Torlak” was recognized as a partner and participated in a technology transfer programme to improve national production capabilities. Preclinical studies conducted in 2013 and 2014 provided comprehensive toxicological evidence supporting the safety of the trivalent influenza vaccine manufacturing platform. Nearly a decade later, this validated platform enabled the independent development of a quadrivalent influenza vaccine. Subsequent preclinical studies conducted in accordance with European Medicines Agency guidelines demonstrated preserved immunogenicity despite the inclusion of an additional antigen. Methods: Preclinical evaluation included standard safety and immunogenicity assessments in animal models. Safety assessment included evaluation of systemic parameters (general health status, leukocyte profile, blood biochemistry, and histopathology) and local reactions. Immunogenicity of both trivalent and quadrivalent formulations was assessed using haemagglutination inhibition and microneutralization assays. Results: No significant systemic or local adverse effects were observed. Both trivalent and quadrivalent formulations induced robust immune responses, with immunogenicity comparable to that of corresponding commercial vaccines. Conclusions: These findings confirm the safety profile and demonstrate strong immunogenicity for both the trivalent and quadrivalent formulations, supporting the successful establishment of a national influenza vaccine platform, contributing to increased pandemic preparedness and sustainable influenza vaccine production.

Vaccines doi: 10.3390/vaccines14060476

Authors: Arvind Singh Kaulsay Nurshariza Abdullah Nur Amelia Azreen Adnan

As a cornerstone of modern science, cell lines are the foundational platforms for key medical advances. They enable vaccinology (through viral propagation and attenuation), gene therapy (via vector development), and biopharmaceutical production (via recombinant protein expression). Designer mammalian, avian, and insect expression systems, including Vero, MDCK, HEK293, BHK21, CHO, PER.C6, EB66, and Sf21/Sf9, have become indispensable cellular platforms, delivering enhanced biologic yields, superior genetic stability, and validated end-product biosafety. Simultaneous advances in cell culture media optimization have enabled a critical shift from serum-dependent media to serum-free, chemically defined, and xeno-free alternatives, which aim to restore compositional traceability of culture media components, reduce potential residual xenogeneic proteins in serum-supplemented media, and promote reproducibility even at the molecular level. This review emphasizes the far-reaching influence of cell culture systems as the expression powerhouse that sustains modern virology, whilst focusing on recent cell-engineering methods and optimization strategies in culture media that have facilitated this shift.

Vaccines doi: 10.3390/vaccines14060475

Authors: Michael Har-Noy

Chronic respiratory diseases (CRDs) represent a significant global mortality burden, largely driven by viral-triggered exacerbations. In the elderly, susceptibility to viral pathogens is critically linked to the “interferon gap”—a kinetic delay in innate antiviral signaling resulting from immunosenescence and Th2-skewed inflammaging. While traditional vaccines provide pathogen-specific protection, their efficacy is often compromised by age-related immune hyporesponsiveness and antigenic drift. This perspective paper proposes a dual-phase, virus-agnostic immunomodulatory platform designed to restore mucosal immune competence and provide a rapid-response intervention for incipient exacerbations. Rather than acting as a pathogen-specific vaccine, the platform serves as a comprehensive host immune-rejuvenation engine and cellular adjuvant platform. The platform consists of two integrated stages: Allopriming and Alloantigen Inhalation Recall (AIR). Allopriming utilizes AlloStim® (activated, allogeneic Th1 cells) to leverage the evolutionarily conserved allo-rejection response, establishing a lung mucosal reservoir of allo-specific Th1 tissue-resident memory cells (Trm). Building on previously published Phase I/II data showing that Allopriming reverses biomarkers of immunosenescence and sustains durable heterologous antiviral responsiveness, the AIR strategy is introduced as a patient-administered rescue mechanism for frail CRD patients. AIR is designed to activate pre-positioned Trm cells at the earliest onset of symptoms, inducing a high-magnitude IFN-γ surge in the lung mucosa. By bridging the senescent “interferon gap” with the rapid effector kinetics of Trm activation, this approach represents a novel paradigm toward reconstituting youthful-like antiviral mucosal immunity to both enhance vaccine efficacy in the elderly and protect against both seasonal pathogens and emerging viral triggers (“Disease X”) of CRD. Future randomized studies in long-term care settings are planned to evaluate clinical outcomes in high-risk populations.

Vaccines doi: 10.3390/vaccines14060474

Authors: Niven Wang Abdelrahman Yousef Kevin Nguyen Timothy Mok Mahmoud Yousef Ahmed Telbany Abu Baker Sheikh Christopher Chang Swathi Paleti

Introduction: Live attenuated vaccines (LAVs) are generally avoided in patients with inflammatory bowel disease (IBD) receiving immunomodulatory therapy due to concerns about infection risk. However, real-world data evaluating their safety in this population remain limited. We aimed to assess adverse outcomes following LAV administration in IBD patients treated with biologic agents. Methods: We conducted a retrospective cohort study using the TriNetX multi-institutional database. Adults with IBD receiving immunomodulatory therapy were categorized into two cohorts: those who received an LAV and those who did not. Biologic therapies included tumor necrosis factor inhibitors (infliximab, and adalimumab), integrin antagonists (vedolizumab), interleukin (IL)-12/23 inhibitors (ustekinumab), IL-23 inhibitors (risankizumab, and guselkumab), and Janus kinase inhibitors (tofacitinib, and upadacitinib). LAVs included measles–mumps–rubella (MMR), varicella (Varivax), and yellow fever vaccines. Propensity score matching was performed based on age, sex, IBD subtype (Crohn’s disease vs. ulcerative colitis), and biologic class. Patients with outcomes prior to the risk window were excluded. Adverse outcomes within six months included hospitalization, emergency department (ED) visits, fever, rash, and encephalitis. Results: A total of 672 patients were included in each propensity-score-matched cohort. Live attenuated vaccine (LAV) administration was not associated with significantly increased adverse outcomes compared with no LAV exposure during the six-month follow-up period. Hospitalization occurred in 14.9% versus 15.3% of patients, respectively (risk ratio [RR] 0.97; 95% confidence interval [CI] 0.75–1.25; p = 0.819), while emergency department visits occurred in 12.6% vs 11.3% (RR 1.12; 95% CI 0.84–1.50; p = 0.450). There were no significant differences in fever (3.6% vs. 3.3%; RR 1.09; 95% CI 0.62–1.93; p = 0.764) or rash (4.0% vs. 2.7%; RR 1.50; 95% CI 0.83–2.70; p = 0.172). No cases of measles, mumps, rubella, varicella, yellow fever, or encephalitis were identified in either cohort during follow-up. Conclusions: LAVs were not associated with an increased risk of adverse outcomes within one day to six months among IBD patients receiving immunomodulatory therapy. These real-world findings suggest comparable short-term outcomes between the cohorts of patients with IBD receiving biologic or targeted synthetic therapy who met the predefined eligibility criteria including age ≥ 18 years, and vaccination occurring between two weeks and six months after biologic initiation regarding LAV use in patients with IBD receiving biologic agents.

Vaccines doi: 10.3390/vaccines14060473

Authors: Vishrut Shah Joseph Todd Martins

Therapeutic cancer vaccines represent a rational immunotherapeutic strategy aimed at inducing tumor-specific adaptive immune responses in patients with established malignancies. In contrast to prophylactic vaccines, these approaches must function within immunosuppressive tumor microenvironments characterized by antigenic heterogeneity, immune dysfunction, and dynamic tumor evolution. Effective vaccine design requires the integration of three essential components: the selection of appropriate tumor-associated or tumor-specific antigens, efficient delivery platforms that enable antigen presentation, and adjuvant systems that promote robust T-cell priming and expansion. Initial clinical investigations in B-cell malignancies and multiple myeloma demonstrated that idiotype-based vaccines can elicit tumor-specific immune responses. However, durable clinical benefit has been inconsistent, reflecting limitations in antigen selection, suboptimal immunogenicity, and tumor-mediated immune evasion. Over the past decade, advances in tumor genomics, next-generation sequencing, and immune monitoring have enabled the development of next-generation vaccine platforms, including dendritic cell-based approaches, personalized neoantigen vaccines, and mRNA-based technologies. Emerging evidence suggests that vaccine efficacy is highly dependent on disease context. Biologically favorable settings such as minimal residual disease (MRD) and post-transplant immune reconstitution provide reduced tumor burden and improved immune competence, thereby enhancing the likelihood of effective immune priming. In parallel, combination strategies incorporating immune checkpoint inhibitors, immunomodulatory agents, and cellular therapies are increasingly being explored to overcome tumor-induced immunosuppression. This review synthesizes current knowledge of therapeutic cancer vaccines in B-cell malignancies and multiple myeloma, with emphasis on immunologic mechanisms, antigen selection, vaccine platforms, and clinical evidence. We further propose a conceptual framework integrating tumor biology, immune context, and combination strategies to guide the rational development of next-generation vaccine therapies.

Vaccines doi: 10.3390/vaccines14060472

Authors: Shinji Fukushima Akira Nishizono Takehiro Hashimoto Atsuo Hamada

The authors would like to make the following corrections to this published paper [...]

Vaccines doi: 10.3390/vaccines14060471

Authors: Amy W. Law Danielle C. Mayer Marjan Zakeri Nehir Yapar Alexandra Passarelli Onur Baser Pia D. M. MacDonald

Background/Objectives: Respiratory syncytial virus (RSV) is the leading cause of infant hospitalizations in the United States. Prevention strategies are recommended to mitigate severe RSV outcomes. In addition to identifying potential coverage gaps, preventative administration timing is important for estimating product effectiveness. This study characterized administration timing of maternal and infant immunization against RSV across the United States during the 2024–2025 RSV season. Methods: A retrospective cross-sectional study was conducted using administrative claims of a commercially insured population from Kythera Labs. Pregnant individuals who received RSVpreF vaccine and infants who received nirsevimab were included. The seasonal cohort included infants born during the RSV season, while infants born from April to September were considered as the catch-up cohort. Baseline characteristics and calendar month and age at immunization (gestational age for RSVpreF) were evaluated. Results: Overall, 37,686 (71.9%) of maternal vaccinations were administered at 32–34 gestational weeks and 92.7% of all vaccinations occurred ≥14 days before delivery. Among infants who received nirsevimab, 34.8% of the seasonal cohort were immunized within 1 week of birth and 33.4% of the catch-up cohort were immunized in October 2024. Conclusions: Most maternal RSVpreF vaccinations occurred early in the recommended eligible gestational age window, while only approximately one-third of infants received nirsevimab during the first week of life or at the beginning of the RSV season. These findings highlight the importance of timely administration of RSV preventives. They further demonstrate that immunization timing should be incorporated into evaluation of the effectiveness and population level impact of RSV prevention programs.

Vaccines doi: 10.3390/vaccines14060470

Authors: Adem Karbuz Tuğce Tural-Kara Ümit Çelik Belgin Gülhan Ayşegul Elvan-Tüz Yasemin Coşgun Çigdem Kirmaci Ayşe Kübra Açık Merve Kılıç-Çil Saliha Kanık-Yüksek Dilek Yılmaz-Çiftdoğan Merve Zerey-Albayrak Vildan Şahin Tuğba Erat Şilem Özdem-Alataş Ekrem Sağtaş Erdem Öksüzoğlu Muhammed Emin Demirkol Ateş Kara

Background/Objectives: Hand, foot and mouth disease (HFMD) has recently emerged as a serious health threat, as certain serotypes can cause severe illness. Serotype distribution vary by region, and seroprevalence studies helps in developing preventive strategies. This study aimed to determine the seroprevalence of enterovirus type 71 (EV-A71), Coxsackievirus A16 (CV-A16), Coxsackievirus A10 (CV-A10), and Coxsackievirus A6 (CV-A6), the main causative agents of HFMD and to investigate risk factors for seropositivity. Methods: This multicenter, cross-sectional study was conducted across five major cities in Türkiye. Children (6 months–17 years) who presented to outpatient clinics for any reason were included between May 2024 and January 2025. Neutralizing antibodies were measured using a microneutralization assay. Statistical analyses included descriptive methods, appropriate group comparisons (Chi-square/Fisher’s Exact), and backward logistic regression to identify factors associated with HFMD seropositivity. Results: The study included 998 participants (mean age: 8.6 ± 5.2 years; 51.3% male). CV-A6 antibodies were detected in 68.5%, EV-A71 in 66.5%, CV-A10 in 60.2%, and CV-A16 in 46.0% of samples. No viral antibodies were detected in 5.3% of serum samples (All-Negative group); antibodies against at least one HFMD agent were detected in 94.7% (Any-Positive group). HFMD seropositivity increased significantly with age. Handwashing habits did not differ between the groups. The any-positive group more often had a household member aged 12–18 years, a mother with lower education, and higher kindergarten attendance. In logistic regression analysis, age, average monthly household income, and mother’s education level were the factors influencing seropositivity. Conclusions: The seroprevalence of HFMD-causing viruses in Türkiye is high from six months of age onward. Beyond promoting personal protective measures, the implementation of a vaccination program should also be considered.

Vaccines doi: 10.3390/vaccines14060469

Authors: Ziying Goh Yi Ling Eileen Koh Wai Keong Aau Ngiap Chuan Tan Chirk Jenn Ng Chung Wai Mark Ng

Background/Objectives: Influenza vaccination in young children reduces the incidence of influenza-related complications. Compared to other vaccines in the Singapore National Childhood Immunization Schedule (NCIS), there is low influenza vaccine uptake rate among young children. Our retrospective database study aimed to evaluate the effect of aligning childhood influenza vaccination to coincide with specific well-visits in the primary care setting. Methods: A retrospective interrupted time series study was conducted on two cohorts of children aged 6 to 12 months (n = 10,082 before, and n = 9234 after). The delivery schedule was aligned with routine touchpoints to administer Dose 1 of the influenza vaccine at the 6-month well-visit and Dose 2 at the 7-month visit. Results: Dose 1 influenza vaccination rates increased from 4.7% before the intervention to 73.7% after the intervention. The proportion of children who completed two doses of the influenza vaccines increased from 3.6% to 62%. Median age at Dose 1 influenza vaccine, and completion of two doses of influenza vaccine decreased from 8.7 to 7.6 months and 9.9 to 7.7 months, respectively. Conclusions: Aligning influenza vaccination with specific well-visits substantially improves uptake, completion rates, and timeliness of vaccination, demonstrating a scalable system-level strategy to enhance immunization coverage in primary care.

Vaccines doi: 10.3390/vaccines14060468

Authors: Linus G. Weber Larissa Dörr Caroline Stephan Leon Freitag Leander John Ingo Jordan Michael W. Wolff

Background: Modified Vaccinia Ankara (MVA) vectors are highly immunogenic vaccine platforms for the delivery of recombinant antigens. Efficient downstream processing is still challenging, particularly because substantial fractions of the virus remain intracellular. While chemical cell lysis that releases MVA particles into the supernatant before clarification can greatly enhance process efficiency and scalability, this step remains insufficiently characterized. Methods: This study assessed the compatibility of ionic, non-ionic, and zwitterionic detergents with the virus as purification target. Polysorbate 20 (Tween 20) was selected as a candidate detergent and evaluated across harvest times of 48–72 h post-infection (hpi) at concentrations of 0.01–0.5% (v/v). Results: The addition of 0.01% to 0.05% Tween 20 at 48 hpi resulted in a twofold increase in supernatant virus within one hour of application. Extended exposure to Tween 20, combined with a 650 mM mixture of NaCl, NaBr, and KCl, promoted virus particle release. However, Tween 20 concentrations above 0.1% reduced MVA infectivity. A filtration cascade using pore sizes of 5 µm and 1.2 µm achieved product yields of 77–83% at 48 hpi and 41–69% at 72 hpi, respectively. Host-cell DNA is an important contaminant during viral vector processing. However, the application of 0.05% (v/v) Tween 20 resulted in a 35% reduction of dsDNA released into the culture supernatant; the nuclei could not be preserved intact under high-salt conditions to avoid the release of cellular DNA. Conclusions: In summary, this comprehensive data demonstrated that non-ionic detergents can be used to induce cell lysis while maintaining infectious activity of enveloped MVA.

Vaccines doi: 10.3390/vaccines14060467

Authors: Joaquín Williman Gonzalo Tomas Ariel Vagnozzi Claudia Techera Sebastián Brambillasca Ruben Pérez Ana Marandino

Background/Objectives: Serial passage in embryonated eggs is widely used to attenuate the infectious bronchitis virus (IBV) for vaccine production; however, the evolutionary processes underlying attenuation and immunogenicity remain incompletely understood. Here, we analyzed genome-wide viral evolution during serial passages to investigate how mutations emerge, persist, are lost, or become fixed over time and how these dynamics relate to changes in pathogenicity and immunogenicity. Methods: Deep sequencing was performed on 11 representative serial passages (P2–P79) of the UY/11/CA/18 strain, including two derivative lineages: P7 VIR (virulent) and P53 VAC (attenuated and immunogenic). Results: This study identified an early adaptive phase characterized by a limited set of mutations potentially associated with genome replication, viral RNA processing, and virion assembly, including a key change in non-structural protein 14 and variants in M and 3c (E). This phase was followed by a broader expansion of the variant spectrum across replicase genes and delayed accumulation of Spike protein variants. Most Spike changes emerged during later passages and exhibited transient dynamics, and only a subset reached a high frequency after the establishment of early replicase- and structural-associated changes. Consistent with these dynamics, P7 VIR diverged before the late accumulation of Spike variants and retained a pathogenic phenotype, whereas P53 VAC diverged after the emergence of early high-frequency variants but before the extensive late-stage Spike variation observed in P79, which was associated with reduced immunogenicity. Conclusions: These findings support a multi-step model of IBV attenuation in which progressive filtering of genome-wide variation shapes distinct evolutionary outcomes during serial passages. This evolutionary framework provides insight into the relationship between attenuation and immunogenicity and may help guide the rational design of live attenuated vaccines.

Vaccines doi: 10.3390/vaccines14060466

Authors: Dieter Volc Caroline Thun-Hohenstein Sabine Schmidhuber Markus Mandler Achim Schneeberger

Background/Objectives: Parkinson’s disease (PD) is a major neurodegenerative disorder with no cure. The goal is to develop an active immunotherapy targeting aggregated alpha synuclein (aSyn), the root cause of PD. TRB-001 is the lead candidate of a novel class of vaccines. It is a peptide/protein conjugate coupled to sugar residues, which is used to target and activate antigen-presenting cells, and addresses aSyn. Methods: A 33-year-old male, diagnosed with PD seven years previously, with a Hoehn & Yahr stage of 1, taking Levodopa/Benserazide (100/25 mg, 6× per day), Rotigotine (8 mg) and Rasagiline (1 mg), amounting to a Levodopa equivalent daily dose (LEDD) of 940 mg, also complicated by impulse control disorder, requested experimental therapy. He received a total of four TRB-001 administrations (weeks 0, 4, 8 and 34) following informed consent. The workup included safety, immunological and clinical parameters. Results: Vaccinations were well tolerated. They induced a high-titer aSyn-specific antibody (Ab) response. Titer increase was associated with a reduction in aSyn plasma levels, suggesting target engagement. The Ab titer and the reduction in aSyn plasma levels were both long-lived. The boost elicited a recall-type Ab titer increase and triggered avidity maturation (factor 7.8). Abs demonstrated a high degree of selectivity for aggregated aSyn (factor 30). Moreover, they were found to preferentially react with tissue from PD brain lysates. The Movement Disorder Society-Sponsored Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) score for the patient remained essentially stable throughout the observation period of 53 weeks. At the time of the boost, the symptomatic PD therapy was simplified to Levodopa/Carbidopa/Entacapone 100/25/200 mg four times a day, amounting to an LEDD of 532 mg. This put an end to the symptoms of the impulse control disorder. Conclusions: Results obtained suggest that this new class of vaccines may yield Ab responses comparable in magnitude and target avidity to the therapeutic setting of monoclonal Abs. TRB-001 is currently being translated to a randomized, placebo-controlled Phase 1B study.

Vaccines doi: 10.3390/vaccines14060465

Authors: Rosaria Iardino Danilo Cereda Simona Scarioni Elisa Sala Francesco Cervellera Sara Russo Riccardo Vecchio Maria Virginia Coscarelli Giuliano Rizzardini Alessandro Venturi Luisa Brogonzoli Catia Rosanna Borriello Anna Odone

Background: In the context of a multi-stakeholder program promoted by Regione Lombardia in collaboration with Fondazione The Bridge and the University of Pavia, the present study investigates the organization and availability of hospital-based vaccination services for high-risk patients. Framing hospitals as strategic hubs for vaccination delivery, the study aimed to map service availability, operational settings and dedicated pathways across the region. Methods: A structured questionnaire was administered in 2025 to 40 healthcare organizations, encompassing 114 hospital facilities, including Local Health and Social Care Authorities (ASSTs) and both public and private Scientific Institutes for Research, Hospitalization and Healthcare (IRCCSs). Descriptive and inferential statistical analyses were performed, and findings were compared with those from the 2023 and 2024 editions of the same survey, developed within the “Vaccination—an opportunity for high-risk patients” project, using Pearson’s chi-square test. Results: In 2025, 99 facilities (86.8% of respondents) reported providing vaccination services for at-risk individuals. Dedicated vaccination pathways were generally available in more than 50% of facilities for nearly two-thirds of the risk categories considered. Vaccination services for diabetic patients were available in 70.7% of facilities. Among healthcare workers, influenza (93%) and SARS-CoV-2 (89.5%) vaccines were the most frequently offered, with rates approximately ten percentage points higher than those of other vaccines. Conclusions: Overall, these findings indicate a regional model progressively consolidating hospital-based vaccination for high-risk groups, with a consistent upward trend in service availability from 2023 to 2025.

Vaccines doi: 10.3390/vaccines14060464

Authors: Subhash Thuluva Subbareddy Gunneri Siddalingaiah Ningaiah Vijay Yerroju Rammohan Reddy Mogulla Kamal Thammireddy Chirag Dhar Shivani Desai Piyush Paliwal Chandrudu Loka Nagaganesh Balne Suresh Kommanapalli Chinmayi Joshi Kishori Sharan Agarwal Girish P. Charde Manish Narang Jai Prakash Narayan Bheemisetty S. Chakravarthy Niranjana S. Mahantshetti Pramod Prabhakar Jog Prashanth Madapura Virupakshappa Savita Verma Madhukar Pandey Pareshkumar A. Thakkar

Background: Pneumococcal conjugate vaccines (PCVs) have substantially reduced pneumococcal disease in children; however, serotype distribution varies geographically, and residual disease due to non-PCV13 serotypes persists. Biological E’s PNEUBEVAX 14® (BE-PCV14), a WHO-prequalified 14-valent PCV, expands coverage by including serotypes 22F and 33F. As PCVs are co-administered with routine Expanded Programme on Immunization (EPI) vaccines, post-licensure data on safety, co-administration, and lot-to-lot consistency are essential. This multicenter phase IV study evaluated BE-PCV14 in healthy PCV-naïve infants aged 6–8 weeks across 31 sites in India. Methods: A total of 2600 infants were enrolled and vaccinated at 6, 10, and 14 weeks of age; 2300 received BE-PCV14 and 300 received PCV13. All participants received concomitant DTwP-HepB-IPV-Hib and oral rotavirus vaccines per routine schedule. Safety was assessed through solicited and unsolicited adverse events (AEs) and serious adverse events (SAEs). Immunogenicity subsets evaluated responses to co-administered vaccines and serotype-specific responses across three BE-PCV14 lots. Results: Among 2600 vaccinated infants, at least one AE occurred in 26.35% (95% CI: 24.59, 28.19) of BE-PCV14 and 24.67% (95% CI: 20.13, 29.84) of PCV13 recipients; most were mild. Injection-site pain and pyrexia were the most common events. Immune responses to co-administered vaccines were comparable between groups and met the non-inferiority criteria: lower bound of the two-sided 95% CI > −10 percentage points for seroprotection/seroconversion rate differences using the Farrington–Manning method. Lot-to-lot consistency was demonstrated, with all GMC ratios within the predefined equivalence margin (0.5–2.0). Conclusions: BE-PCV14 was well tolerated. Immune responses to co-administered routine EPI vaccines met predefined non-inferiority criteria, supporting the interpretation that BE-PCV14 did not result in clinically meaningful immune interference. Consistent immune responses across manufacturing lots further support its use in infant immunization programs.

Vaccines doi: 10.3390/vaccines14060463

Authors: Muneera Anwer Rifat Rahman

Cancer vaccines represent a promising strategy in cancer immunotherapy by inducing tumour-specific immune responses. However, their clinical efficacy remains limited due to challenges in antigen selection, including the distinction between self and non-self-antigens, as well as issues related to antigen delivery, immune activation, and tumour immune evasion. Advances in nanotechnology have introduced innovative approaches to improve vaccine stability, targeted delivery, and immunogenicity. Nanoparticle-based platforms, including lipid, polymeric, inorganic nanoparticles, and virus-like particles, enable efficient delivery of tumour antigens and immunostimulatory adjuvants to antigen-presenting cells, thereby enhancing adaptive immune responses. Despite these advances, several translational challenges persist, including immunosuppressive tumour microenvironments, inefficient lymph node targeting, safety concerns, and manufacturing limitations. This review summarizes key nanoparticle platforms used in cancer vaccine development and discusses major barriers to their clinical translation. We also emphasize platform-selection criteria, cargo-dependent carrier design, nanoparticle size constraints, engineering strategies used to improve cytosolic delivery and endosomal escape, and the current clinical pipeline of cancer nanovaccines. Additionally, emerging strategies such as personalized nanovaccines, mRNA vaccine platforms, and combination immunotherapies are highlighted as promising approaches to improve therapeutic efficacy. These advances are expected to accelerate the clinical translation of nanotechnology-enabled cancer vaccines and support the development of next-generation cancer immunotherapies.

Vaccines doi: 10.3390/vaccines14050462

Authors: Md. Abdus Salam Md. Yusuf Al-Amin Kasireddy Sudarshan Aidan Lynch Victor Reyes Madeline Stevenson

Next-generation vaccines are being developed to elicit durable and cross-protective immune responses against diverse pathogens, particularly those targeting the respiratory and enteric systems. By strategically engaging T cell-centric antigen design, mucosal immune engagement, and induction of trained innate immunity, these innovative platforms are expected to reshape the paradigm of immunoprophylaxis and to offer promising avenues for enhanced protection against complex infectious diseases. Conventional antibody-based vaccines, though effective against many infections, often lack the capacity to induce durable or cross-protective immunity at mucosal surfaces. Advances in antigen design, delivery platforms, and adjuvant technologies now facilitate precise activation of tissue-resident memory T cells and enhancement of mucosal secretory IgA responses, thereby achieving sterilizing immunity at barrier surfaces while reinforcing systemic immune protection. Advanced delivery platforms, including lipid nanoparticles, viral vectors, and nano or liposomal carriers, further refine antigen presentation, enhancing stability, targeting, and overall immunogenicity. Concurrently, progress in understanding trained innate immunity highlights opportunities to induce broad, non-antigen-specific protection through epigenetic and metabolic reprogramming of innate cells. The integration of these adaptive and innate mechanisms may enhance early pathogen control, limits transmission, and strengthens defense against variant and antimicrobial-resistant pathogens across diverse populations. However, translating these immunological insights into safe, scalable, and globally accessible vaccines remains a major challenge. This review explores the emerging conceptual framework of next-generation vaccines that demonstrate partial integration of these axes in preclinical models, though human translation and functional synergy require Phase II validation. It highlights progress toward next-generation vaccines leveraging integrated adaptive and innate immune reprogramming for superior protection against respiratory and enteric pathogens.

Vaccines doi: 10.3390/vaccines14050461

Authors: Jagmohan Singh Taranjot Johar Vannessa Scully Scott A. Waldman Babar Bashir Adam E. Snook

Background: Live-attenuated Listeria monocytogenes (Lm) vectors are a clinically validated cancer immunotherapy platform, but translation requires reproducible, clinically realistic workflows for dose preparation and infusion. For live bacterial products, in-use stability and device compatibility can drive dose variability through adsorption, settling, and device losses. Methods: We developed and GMP-manufactured an attenuated Lm vaccine expressing human GUCY2C (Lm-GUCY2C) and performed translational characterization, including construct verification and immunogenicity readouts, and defined the administration-focused in-use stability and device compatibility. Post-thaw stability was assessed in primary cryovials and during preparation and delivery from 250 mL saline infusion bags using standard clinical devices (syringes/needles, filter-free IV tubing) and OnGuard2 closed-system components. Samples were collected over 24 h at room temperature, and viable Lm-GUCY2C were quantified by CFU recovery. Results: Lm-GUCY2C remained stable in thawed cryovials for 24 h with no significant CFU loss. High-dose infusion bags (3 × 109 CFU/bag) maintained CFU recovery through 6 h, whereas low-dose bags (3 × 108 CFU/bag) exhibited significant losses beginning at 3 h, supporting a practical in-use window of up to 2 h for low-dose preparations. OnGuard2 intravenous (i.v.) connectors did not measurably affect CFU recovery, while OnGuard2 vial adapters reduced recovery. Conclusions: This work provides an end-to-end, translationally focused characterization of a GMP-manufactured Lm cancer vaccine, including clinically actionable in-use handling constraints and device compatibility. These data define preparation and administration guardrails (notably, time-to-infusion limits for low-dose bag preparations) that can improve dose accuracy and reproducibility in clinical testing.

Vaccines doi: 10.3390/vaccines14050460

Authors: Jesús de la Fuente-Valero Javier Rejas-Gutiérrez Marta del Pino Carmen González-Granados Raquel Oliva-Sánchez Beatriz Procas-Ramón Mar Ramírez-Mena Aaron Cohen-Castiel Javier Calvo-Torres María Fasero Pluvio J. Coronado on behalf of the HPV-Know Collaborative Group, SPAIN-GOG on behalf of the HPV-Know Collaborative Group, SPAIN-GOG

Background/Objectives: Health outcome determinants affecting Human Papillomavirus (HPV) vaccination among the adult female population are scarce in Spain. This study aimed to describe the health outcomes and determinants of HPV vaccination in women 18–65 years attending lower genital tract outpatient clinics across regions of Spain. Methods: This was a cross-sectional, multicenter, non-interventional, descriptive, and comparative nationwide study. Sociodemographic characteristics and health outcomes included obstetric, gynecological and HPV vaccination antecedents, together with patient-reported outcomes related to HPV infection. Statistical analysis included multivariate logistic regression models. Results: Among 2004 adult women recruited, 1907 (95.2%) were eligible for analysis. Vaccine uptake was 48.8%; 81.6% among women who were ever HPV positive (adjusted OR = 2.16 [95% CI: 1.59–2.93], p < 0.001), but 65.9% among women with an active infection, which acted as a negative factor for vaccination (OR = 0.63 [0.45–0.87], p = 0.005), as did increasing age (OR = 0.92 [0.90–0.93], p < 0.001); the higher the age, the lower the adjusted likelihood of being vaccinated. HPV knowledge and adequate physician-provided information were weakly associated with vaccination likelihood. A history of conization (OR = 7.48 [5.34–10.47], p < 0.001), use of contraception (OR = 1.49 [1.13–1.96], p = 0.004), infection with high-risk or unknown-risk HPV genotypes (OR = 1.86 [1.23–2.82], p = 0.003 and OR = 1.68 [1.17–2.42], p = 0.006, respectively), and Spanish nationality (OR = 2.46 [1.68–3.61], p < 0.001) were identified as factors associated with a higher vaccination likelihood. Conclusions: This study found that HPV vaccination uptake is improvable. Previous HPV infection favored vaccination; however, active infection and increasing age acted against vaccination. HPV knowledge and adequate healthcare professional information appeared to favor vaccination, along with, most notably, a history of cervical surgery (conization), contraceptive use, or infection with high-risk or unknown-risk HPV genotypes. Spanish women had a higher likelihood of receiving HPV vaccination than foreign residents.

Vaccines doi: 10.3390/vaccines14050459

Authors: Harriet Oboge Wei-Chiao Huang Gabriel Aboge Hannah Chege Rose Ojuok Naomi Chege Joel Musando Elizabeth Jane Poole Samuel Mwangi Thumbi Vishvanath Nene Jonathan F. Lovell Anna Lacasta

Background: Effective vaccines are essential to overcome the limitations of livestock immunisation, particularly in low- and middle-income countries (LMICs), where scalable, thermostable, and easy-to-administer solutions are needed. Nanoparticle-based delivery systems, such as the Spontaneous Nanoliposome Antigen Particle (SNAP) technology using CoPoP liposomes, offer a promising alternative for subunit vaccine development, although their performance in large animal species remains poorly characterised. CoPoP enables the rapid non-covalent multimeric display of His-tagged protein antigens combined with immunomodulators on liposomes incorporating cobalt porphyrin–phospholipid (CoPoP). Objective: To evaluate the immunogenicity of CoPoP-based liposomes delivering the Theileria parva p67C antigen in cattle and compare their performance in murine models. Methods: Cattle and mice were immunised with p67C formulated in CoPoP liposomes incorporating QS-21 and/or PHAD immunomodulators. Humoral and cellular responses were assessed. Parallel in vitro stimulation of bovine PBMC with Quil-A was used to investigate the mechanistic effects of saponins on bovine cells. Results: CoPoP liposome formulations did not improve p67C immunogenicity in cattle, with antibody responses at least two-fold lower than previously reported results and no detectable cellular responses. In contrast, the same platform induced up to 2000-fold higher antibody titres in mice. This disparity is likely driven by differences in antigen dose relative to body mass, tissue architecture, lymphatic accessibility, and innate immune signalling differences. PHAD-mediated TLR4 activation appeared less effective in cattle, whereas QS-21 induced a broader immune activation, likely through conserved inflammasome pathways. Despite limited immunogenicity, antigen presentation by CoPoP liposomes was preserved. Conclusions: SNAP-based CoPoP liposomes showed strong immunogenicity in mice but limited efficacy in cattle, highlighting the challenges of cross-species translation. Optimisation of antigen dose and adjuvant selection for the targeted species is required, with QS-21 representing a more promising candidate than the TLR4 agonist. The scalability and versatility of SNAP technology support its continued development for multivalent livestock vaccines.

Vaccines doi: 10.3390/vaccines14050458

Authors: Ilias Pagkozidis Georgios Papazisis Anna-Bettina Haidich Zoi Tsimtsiou

Background/Objectives: Primary Care Physicians (PCPs) are widely regarded as trusted sources of health information and can play a pivotal role in increasing seasonal influenza vaccination (SIV) within their communities. We aimed to explore PCPs’ attitudes toward SIV and their views regarding proposed strategies to enhance SIV uptake in the evolving post-pandemic landscape. Methods: A qualitative study utilizing semi-structured individual interviews with a nationwide sample of 25 PCPs was conducted. Results: Physicians’ attitudes toward SIV were overwhelmingly positive; they recognized its protective value for individuals and the community alike, its efficacy in averting serious illness, and its proven safety profile. Regarding strengthening SIV uptake, PCPs positively appraised the following strategies: (a) viewing all clinical encounters as opportunities for vaccination; (b) outsourcing vaccination to nursing, allied health staff and community pharmacists, provided that specific prerequisites are met; (c) forwarding personalized notifications to health providers and (d) the public; and (e) establishing at-home vaccinations. Financial incentives would reportedly act as tangible acknowledgement and motivate PCPs to work toward primary prevention. However, others have argued that SIV is inherently embedded in their duty as PCPs, and potential remunerations would dwindle the public’s confidence in PCPs. Establishing incentives for the general population reportedly minimizes confidence and the perceived value of SIVs and was assessed to be ineffective in the Greek context. Promoting SIVs through video games was considered to be less effective for the adult population. Conclusions: Mapping PCPs’ insights is key in designing effective SIV strategies that are concurrent with communities’ values, needs, and learnt experience from the COVID-19 pandemic.

Vaccines doi: 10.3390/vaccines14050457

Authors: Chunna Ma Jiaojiao Zhang Jiaxin Ma Wei Duan Yingying Wang Xiaodi Hu Jia Li Lu Zhang Yuanzhi Di Shuning Yan Peng Yang Quanyi Wang Ying Shen Daitao Zhang

Background: Data on influenza vaccine effectiveness (VE) against hospitalized severe acute respiratory infection (SARI), particularly in Asia, remain limited for the 2025/26 Northern Hemisphere influenza season. This study aimed to evaluate real-world VE against A(H3N2)-associated SARI hospitalization and provide timely, locally relevant evidence to inform seasonal influenza vaccination policy. Methods: A test-negative design was used to estimate VE against influenza A(H3N2)-associated SARI hospitalization in Beijing, China, from 10 November 2025 to 18 January 2026. VE was estimated by comparing the odds of influenza vaccination between case-patients (those who tested positive for A(H3N2)) with controls (those who tested negative for influenza). Results: Among 1883 enrolled SARI inpatients, 220 (11.7%) tested positive for influenza A(H3N2). Overall vaccination coverage was 11.4%, with the highest coverage observed among children aged 5–17 years (29.6%). Influenza positivity was higher among rural residents, patients with pneumonia or hypoxemia, and those with symptom onset in November. The adjusted overall VE was 7.5% (95% CI: −45.8% to 43.3%). Moderate VE was observed among children aged 5–17 years (45.4%, 95% CI: −33.6% to 79.5%), although the confidence interval included zero and the estimate was not statistically significant. Negative VE estimates were observed among younger children and older adults. Among patients with underlying respiratory conditions, VE was 75.4% (95% CI: −27.4% to 98.7%), although this estimate was also not statistically significant. Conclusions: During the 2025/26 influenza season in Beijing, VE against A(H3N2)-associated SARI hospitalization was suboptimal. Moderate protection was observed among children aged 5–17 years, the group with the highest vaccination coverage, but the estimate was not statistically significant. The low overall VE may be attributable to antigenic mismatch between vaccine and circulating strains, as well as low population-level vaccination coverage. These findings highlight the need to improve vaccine formulations and increase vaccination coverage, particularly among adults and older populations.

Vaccines doi: 10.3390/vaccines14050456

Authors: Charlotte Vernhes Kateryna Khmilevska Alexis Caron Emanuele Ciglia Rosybel Drury Judith Perez-Gomez Volker Vetter

Background/Objectives: Vaccine development pipelines are forward-looking indicators of public health preparedness, reflecting the capacity to address unmet medical needs and emerging threats. This descriptive analysis aims to characterise the 2025 clinical-stage pipeline of infectious disease vaccines and prophylactic monoclonal antibody candidates developed by Vaccines Europe member companies, and to describe how pipeline characteristics address evolving public health priorities. Methods: A descriptive analysis was conducted using publicly available data compiled in the Vaccines Europe Pipeline Review 2025, with validation by participating companies. Candidates in clinical development or regulatory review were classified using a standardised framework by pathogen/disease, target population, public health priority, and technologies. Results: The Vaccines Europe member company pipeline comprises 91 candidates across clinical development phases, 19% of which are in Phase III and 7% undergoing regulatory review. This pipeline is predominantly targeting respiratory pathogens (75%), with a strong life-course focus (85% evaluated in adults and/or older adults), and sustained activity in bacterial pathogens relevant to antimicrobial resistance. Notably, 41% of candidates were classified as addressing diseases, disease combinations, or indications for which no licenced preventive product exists. This category includes candidates targeting diseases without a preventive solution, as well as novel combination vaccines and therapeutic approaches in areas where individual components or preventive vaccines are already available. This captures vaccines candidates in different stages of development, not necessarily first-in-disease innovation. The pipeline shows broad technological diversity (12 technologies), dominated by RNA approaches and multivalent candidates, with growing focus on climate-sensitive, zoonotic, and pandemic-prone pathogens. Conclusions: Within the pipeline of Vaccines Europe member companies, this analysis describes development activity oriented toward broader prevention, platform-based approaches, and preparedness-relevant targets. As a structured and recurring annual assessment, the Vaccines Europe Pipeline Review supports horizon scanning and evidence-based dialogue between industry and vaccine ecosystem stakeholders. In order to maximise the impact of vaccine development pipelines to public health, predictable investment, streamlined trial and regulatory pathways, strong surveillance, and real-world data systems, coordinated decision-making is required to enable timely and equitable access, and complementary incentive and procurement reforms.

Vaccines doi: 10.3390/vaccines14050455

Authors: Magdalini Christodoulou Chrisoula Paraforou Erasmia Rouka Aikaterini Toska Dimitrios Papagiannis

Objectives: Despite the critical role fathers play in family health decisions, most research on HPV vaccination focuses predominantly on mothers. This study examines gender differences in HPV knowledge and vaccination attitudes among Greek parents, addressing a significant gap in the literature. Methods: A cross-sectional study using convenience sampling was conducted in waiting rooms of public primary healthcare settings in the Larissa prefecture of central Greece, between September and December 2024. Of 250 distributed questionnaires, 208 were returned (response rate: 83%), of which 192 were eligible for analysis. The analysis compares responses from fathers (n = 42) and mothers (n = 150) regarding HPV knowledge, intentions to vaccinate their sons, and general vaccine attitudes; no explicit restriction to one respondent per family was applied. Statistical comparisons employed chi-square tests, Fisher’s exact test, and binary logistic regression. Results: Fathers demonstrated significantly lower HPV awareness compared to mothers (42.9% vs. 64.0%, χ2 = 10.907, p = 0.004). Vaccination intentions for sons were similar between groups (fathers: 85.7%, mothers: 85.3%, p = 0.540). No statistically robust association between HPV awareness and vaccination intention was identified in either group, likely reflecting the high overall intention rates and limited outcome variability. Binary logistic regression identified female sex as the only significant independent predictor of HPV awareness (OR = 2.26, 95% CI: 1.12–4.58, p = 0.024). Conclusions: While fathers exhibit significantly lower HPV knowledge than mothers, they demonstrate equal willingness to vaccinate their sons. These findings suggest that knowledge gaps do not necessarily translate to vaccine hesitancy, but highlight the need for targeted, father-inclusive health education interventions. Public health programs should actively engage fathers in HPV vaccination discussions to capitalize on their positive vaccination intentions while addressing their information needs.

Vaccines doi: 10.3390/vaccines14050454

Authors: Xuena Du Yuxia Yuan Cong Tang Yanwen Li Zhaolan Guo Yun Yang Hao Yang Yanan Zhou Qing Huang Hongyu Chen Wenqi Quan Junbin Wang Shuaiyao Lu

Background/Objectives: Recurrent influenza epidemics impose a severe global burden, with conventional vaccines constrained by production time lags and rapid viral mutation. This study aims to explore a novel influenza mRNA vaccine design that balances conserved and mutable antigen regions. By combining hemagglutinin (HA) and neuraminidase (NA) into a dual-target approach, the objective is to simultaneously block viral entry and inhibit progeny release, potentially establishing a proposed “front-blockade, rear-containment” dual protective barrier against multiple H1N1 strains. Methods: We engineered a dual-target tandem mRNA vaccine linking mutated HA with conserved NA, with strategic amino acid mutations introduced into key antigenic sites within the HA head domain. Vaccine efficacy was evaluated in a mouse model. Humoral immunity was assessed by measuring antigen-specific antibody titers, and cellular immunity was evaluated via ELISpot assay. Protective capacity was determined through lethal challenge experiments using diverse H1N1 viral strains. Results: The vaccine successfully expressed the HA-NA tandem antigen at 130 kDa, and the in vitro-expressed antigen exhibited normal neuraminidase activity. Preliminary evidence supported the dual-target concept in model mice: hemagglutination-inhibiting and micro-neutralizing antibodies targeting HA were detected, and serum neuraminidase-inhibiting activity was also observed. In addition to triggering potent cellular immune responses, the vaccine offered total protection against lethal doses of various H1N1 variants. Conclusions: This study suggests a promising dual-target strategy that harmonizes antigen conservation and mutation while potentially establishing a synergistic front-blockade and rear-containment defense. The approach offers a viable pathway for developing improved H1N1 influenza vaccines.

Vaccines doi: 10.3390/vaccines14050453

Authors: Raikhan Nissanova Markhabat Kassenov Vladislava Suchshikh Perizat Akshalova Zhandos Abay Vladimir Kirpichenko Aiken Karabassova Saira Kaimoldina Zhibek Zhetpisbay Elvira Bashenova Ainur Nurpeisova

Background: Cervical cancer, largely attributable to persistent infection with high-risk human papillomavirus (HPV), remains a major public health burden worldwide, including in Kazakhstan, where limited screening coverage and low public awareness contribute to substantial incidence and mortality. This study evaluated the cost-effectiveness and epidemiological impact of a nationwide HPV vaccination programme for 10-year-old girls in Kazakhstan using the quadrivalent Gardasil-4 vaccine. Methods: A 10-year modelling analysis (2025–2035) was conducted using the World Health Organization (WHO)-endorsed Universal Vaccination Impact and Cost-Effectiveness Assessment (UNIVAC) tool adapted to Kazakhstan-specific epidemiological and economic parameters. Vaccination coverage was projected at 98.0% for the first dose and 96.5% for the second dose. Incremental cost-effectiveness ratios (ICERs) and disability-adjusted life years (DALYs) averted were estimated from governmental and societal perspectives. Sensitivity analyses assessed uncertainty in vaccine coverage, vaccine costs, and epidemiological inputs. Results: Over the 10-year period, the vaccination programme was projected to reduce HPV-related disease cases by 68.2% (from 112,198 to 35,628) and deaths by 68.3% (from 15,921 to 5056), while averting 67,445 DALYs. The ICER was estimated at US$ 533 per DALY averted from the governmental perspective and US$ 1169 from the societal perspective. Projected healthcare cost savings reached US$ 42.8 million, driven largely by reductions in 21,748 hospitalisations and 13,706 outpatient visits. These findings remained robust in probabilistic sensitivity analysis, with the probability of cost-effectiveness increasing as the willingness-to-pay threshold rose. Conclusions: UNIVAC-based modelling suggests that introduction of a national HPV vaccination programme for 10-year-old girls in Kazakhstan using Gardasil-4 could substantially reduce cervical cancer burden and related mortality while generating considerable healthcare savings. These findings support the cost-effectiveness of nationwide HPV vaccination in Kazakhstan.

Vaccines doi: 10.3390/vaccines14050452

Authors: Kathryn L. Hopkins Sidy Ndiaye Zeinebou Sidi Abdullah Rita Atugonza Ousseynou Badiane Khassoum Ba Tyler Best Jean Claude Bizimana Dah Cheikh Jean Claude Andrianirinarison Eraste Rwagitare Tene-Alima Essoh Nhamo Gonah Stephen C. Hadler Benjamin M. Kagina Leopold Lambou Abdoulaye Mangane Wilberforce Musoga Kabweru Osée Rurambya Sebatunzi Mohamedhen Itawel Oumrou Priscylla Volazandry Lalao Harisoa Ramanandraibe Noeline Ravelomanana Theresa Sommers Lisandro Torre Elisabeth Wilhelm Atakouma D. Yawo Allarangar Yokouide Ronald Wasswa Lassane Kabore

Background/Objectives: Transitions to new vaccines or antigen schedules represent complex system changes requiring coordinated governance, reliable data systems, domestic financing, and multisectoral collaboration. In 2025, African countries were moving toward a switch from separate pentavalent and inactivated poliovirus vaccines to the combined hexavalent vaccine. This project report describes the Hexavalent Vaccine Switch Early Adopters Workshop in Dakar, Senegal, which included ten African countries, and its implications for future vaccine introductions. Methods: We conducted a practice analysis drawing on structured documentation of plenary presentations, country case studies, interactive problem-solving sessions, and national roadmap exercises. A thematic framework aligned to ten process points for the hexa switch guided synthesis. Results: Countries reported shared system vulnerabilities, including coexistence risks of legacy and new vaccine stocks, inconsistent data completeness, under-resourced vaccine safety surveillance, and financing uncertainties. Early adopter countries demonstrated operational feasibility, logistical efficiencies, and opportunities for reducing injection burden. Outputs included a Health System Adaptation Checklist, a Switch Risk Mitigation Catalog, and 12-month national roadmaps. Conclusions: Regional peer-learning mechanisms can accelerate decision-making, improve operational quality, and strengthen accountability for vaccine introductions. Structured cross-country collaborations can transform a product switch into a scalable system-strengthening opportunity.

Vaccines doi: 10.3390/vaccines14050451

Authors: Ari Prayitno Mulya Rahma Karyanti Nina Dwi Putri Pratama Wicaksana Felicia Felicia Shafira Ninditya Sarah Kemalasari Aldila Ardine Hindra Irawan Satari Sri Rezeki Hadinegoro

Background: Streptococcus pneumoniae may asymptomatically colonize the human nasopharynx and remains a leading cause of invasive and noninvasive disease in children, accounting for an estimated 294,000 global deaths in those aged under five years. Nationally representative serotype data from Indonesia remain limited despite national PCV13 rollout in 2022. This study aims to evaluate the distribution of Streptococcus pneumoniae serotypes and estimate the coverage of pneumococcal conjugate vaccines (PCVs) among children aged 0–18 years in Indonesia. Methods: Systematic search of PubMed, Scopus, ScienceDirect, Google Scholar, and Paediatrica Indonesiana (to December 2025) for observational studies (PROSPERO CRD420251239935). The extracted data included the study period, setting, population, specimen type, serotypes, sample size, and nasopharyngeal carriage. Pooled serotype prevalence is calculated; vaccine coverage estimated for pneumococcal conjugate vaccines containing 10 (PCV10), 13 (PCV13), 15 (PCV15), and 20 (PCV20) serotypes assuming vaccine-type priority in multicolonization. Risk of bias assessed using the Joanna Briggs Institute’s checklist for prevalence studies. Results: Nineteen studies across 13 regions of Indonesia involving children aged 0–18 years included. Nasopharyngeal carriage ranged from 21.0% to 87.6% in healthy children and 9.2% to 73% in children with illnesses. The most common serotypes were 19F, 23F, 6B, 14, 19A, and 34. Non-typeable isolates accounted for more than 20% of all isolates in several studies. The pooled coverage for PCV10, PCV13, PCV15, and PCV20 was 40.3%, 50.2%, 50.8%, and 57.0% respectively. Low-moderate RoB (63% low). Conclusions: The dominant serotypes largely included in PCV13. Active surveillance is required to monitor serotype shifts and ensure the long-term effectiveness of the national vaccination program.

Vaccines doi: 10.3390/vaccines14050450

Authors: Nivedita L. Bhushan Rafael Gonzalez Brian G. Southwell

Background: The development of an efficacious preventive human immunodeficiency virus (HIV) vaccine remains a central goal of global HIV elimination efforts, yet biological performance alone will not determine a future vaccine’s public health impact. Method: This review draws on behavioral science, communication research, vaccine implementation, and HIV prevention literature to identify cognitive, social, and structural challenges that are likely to shape public acceptance and uptake of a future HIV vaccine, as well as to outline evidence-based opportunities for addressing them. Results: Based on the available literature, mental models of both HIV and vaccination will be a critical determinant of how communities consider a future vaccine, particularly given that emerging mRNA and adjuvanted platforms may generate side effects that could be easily misinterpreted and that highly effective long-acting pre-exposure prophylaxis (PrEP) options already exist and will shape how individuals evaluate a vaccine’s relative value. HIV-related stigma further complicates this landscape by making vaccination a socially interpreted behavior, unlike some other vaccination efforts. Together, these factors suggest that hesitancy and misalignment between public understanding and scientific evidence are predictable and should be anticipated rather than addressed reactively. At the same time, decades of HIV prevention implementation research have established an evidence base for vaccine communication, and existing community engagement infrastructure offers a foundation upon which future rollout efforts can build. We highlight three evidence-based strategies as particularly promising levers for encouraging acceptance and adoption. Conclusions: We conclude with recommendations for HIV vaccine researchers and healthcare professionals to invest in formative research, build community partnerships in advance of vaccine availability, and pilot integrated delivery models within existing HIV prevention services.

Vaccines doi: 10.3390/vaccines14050449

Authors: Rachael Purcell Margie Danchin Nigel W. Crawford Eric Zhao Ashleigh Rak Michelle L. Giles Jim Buttery

Objectives: Changes in public policy are eroding vaccine confidence. Previously accepted peer-reviewed evidence around vaccination and developmental outcomes for children is being questioned. Robust, methodologically sound safety data are more needed than ever to maintain consumer confidence. Establishing further safety data on infant health, development, and allergies after COVID-19 and influenza vaccination in pregnancy may improve confidence and acceptance. Methods: This is a state-wide multi-centre prospective cohort study conducted as a sub-study of the Generation Victoria birth cohort. It will examine the risk difference for infant health, developmental, and allergy outcomes between groups of mother–baby pairs who will be examined according to exposure (vaccination against a respiratory virus during pregnancy) and comparator (no vaccination against a respiratory virus). Results: Data contributing to the analysis include GenV-collected developmental, health, and allergy outcomes to 12 months of age, as well as data from state-wide linked datasets. Conclusions: This linked-data longitudinal study will provide information on health, allergy, and developmental outcomes for infants in the first year of life after influenza and COVID-19 vaccination during pregnancy. Implications for Public Health: The reporting of developmental data will be a new contribution to knowledge around outcomes after vaccination during pregnancy.

Vaccines doi: 10.3390/vaccines14050448

Authors: Angela Chia-Chen Chen Lihong Ou Elizabeth Reifsnider Kimberly Arcoleo Ashish Amresh Michael Todd

Background/Objectives: Human papillomavirus (HPV) vaccination coverage among adolescents remains below public health targets despite strong evidence of vaccine effectiveness in preventing HPV-related cancers. Digital interventions (e.g., serious games) may improve HPV vaccine uptake, but evidence for effects on vaccination behavior remains limited. Methods: This secondary analysis of a randomized controlled trial evaluated a co-designed, game-based digital intervention to increase HPV vaccine initiation among unvaccinated youth aged 11–14 years and their parents. The sample included 64 parent–adolescent dyads (33 intervention and 31 usual care dyads). The primary outcome was HPV vaccine initiation at 2-month follow-up. Results: A significantly greater proportion of adolescents in the intervention group initiated HPV vaccination compared with controls (88.5% vs. 46.2%; χ2(1) = 10.58, p = 0.001; risk difference = 0.423, 95% CI = [0.196, 0.650]). No significant between-group baseline differences were observed in parent HPV vaccination intention, knowledge, or psychosocial perceptions, although adolescent vaccination intention was higher in the intervention group. In adjusted logistic regression controlling for adolescent baseline HPV vaccination intention, intervention participants remained significantly more likely to initiate vaccination than controls (OR = 9.31, 95% CI = 2.13–40.70, p = 0.003). Intervention acceptability was high, with most parents and adolescents reporting that the game was easy to use, engaging, and relevant to vaccination decision-making. Conclusions: These findings provide preliminary evidence that a brief, family-centered, game-based digital intervention may help increase HPV vaccination initiation among adolescents. Larger trials with longer follow-up are needed to assess vaccine series completion and effectiveness across diverse settings.

Vaccines doi: 10.3390/vaccines14050447

Authors: Soliou Badarou Aimé Serge Dali Kokou Herbert Gounon Lorraine Shamalla-Hannah Amevegbe Kodjo Boko Xavier Richard Sire Erinna Corinne Dia

Introduction: The COVID-19 pandemic disrupted immunization services in Togo, resulting in 69,672 “zero-dose” and 24,846 “under-vaccinated” children by the end of 2023. This study assessed the effectiveness, acceptability, and feasibility of a social marketing approach deployed during the 2025 Big Catch-Up initiative in Togo. Methods: A convergent mixed-methods study was conducted in 17 priority health districts. The quantitative component compared vaccination coverage before and after the intervention using administrative data. Chi-squared test for linear trend compared district-level coverages, and statistical significance was set at p < 0.05 for all tests. The qualitative component used in-depth interviews with key informants to collect data, followed by thematic content analysis. The intervention was grounded on the social marketing framework with 4 pillars (4Ps): Product, Price, Place, and Promotion. Results: Coverage increased dramatically: Penta1 from 1% to 64%, Penta3 from 1% to 45%, MR1 from 4% to 50%, and MR2 from 6% to 49% (all p < 0.001). Togo ranked 3rd out of 24 African countries for Penta1 progress. The approach demonstrated high community acceptability, with Vaccination Monitoring Committees praised as being culturally appropriate. Key concerns included sustainability and resource constraints. Conclusions: Social marketing was associated with increased community adherence and immunization coverage improvement. However, long-term sustainability requires the institutionalization of community structures with domestic funding and continued health system strengthening.

Vaccines doi: 10.3390/vaccines14050446

Authors: Lanxin Jia Ran Qiu Jing Liu Bo Liu Xuanxuan Nian Yang Le Xixin Han Qingmei Zhang Xuedan Li Zheng Gong Ailin Shen Zhegang Zhang Ying Zhao Jiayou Zhang

Objectives: Seasonal influenza leads to substantial global morbidity and mortality, especially in adults aged 65 years and older, who present poor immune responses to standard-dose influenza vaccines. This study aimed to systematically evaluate the preclinical safety and immunogenicity of a high-dose quadrivalent seasonal influenza split vaccine (HD-QIV), providing preclinical evidence for its clinical application in the elderly. Methods: Following GLP guidelines, we performed single-dose and repeated-dose toxicity tests in Sprague–Dawley rats, active systemic anaphylaxis assays in guinea pigs, and immunogenicity assessments in young and aged BALB/c mice. Safety indicators included general clinical signs, hematology, blood biochemistry, histopathology and allergic reactions; immunogenicity was evaluated via hemagglutination inhibition (HI) antibody titers and antigen-specific cellular immune responses. Results: HD-QIV only caused mild and reversible local irritation in rats without obvious systemic toxicity, and no dose-related systemic anaphylaxis was observed in guinea pigs. HD-QIV induced robust and dose-dependent humoral immune responses, and showed significantly higher HI antibody titers, earlier seroconversion and longer antibody persistence than standard quadrivalent influenza vaccine in aged mice. Cellular immunity was slightly enhanced but not the dominant protective response. Conclusions: The HD-QIV demonstrates favorable preclinical safety and superior immunogenicity, supporting its further clinical development and use as a priority vaccine for the elderly population.

Vaccines doi: 10.3390/vaccines14050445

Authors: Lama Alzamil

Background/Objectives: The COVID-19 pandemic disrupted routine immunisation globally. Saudi Arabia presents a unique epidemiological context for measles, combining high vaccination coverage with mass pilgrimages and a large expatriate workforce. This study examined measles incidence trends, vaccination coverage, and demographic and geographic burden distribution in Saudi Arabia (2015–2024), with comparative analysis against GCC countries, the Eastern Mediterranean Region (EMR), and global data. Methods: Annual incidence and vaccination coverage data were obtained from the WHO Global Health Observatory and WHO/UNICEF WUENIC; monthly, regional, age- and nationality-stratified data from the Saudi Ministry of Health Annual Statistical Book (2015–2024). Incidence was expressed per 1,000,000 population across three epochs: pre-COVID-19 (2015–2019), pandemic disruption (2020–2021), and post-COVID-19 rebound (2022–2024). Descriptive analyses included period means, percentage changes, rate ratios, and rate differences. Results: Pre-COVID-19 incidence (mean 19.7/1,000,000) remained below EMR and global averages. The pandemic produced near-complete suppression (−96.6% to 1.1/1,000,000 in 2020), exceeding global (−82.2%) and EMR (−61.2%) declines. A marked rebound occurred in 2023 (67.8/1,000,000), surpassing the pre-pandemic peak despite MCV1/MCV2 coverage above 96%. Non-Saudi nationals bore disproportionate burden in 2021 (20.7 vs. 1.1/1,000,000) and 2023 (70.4 vs. 64.8/1,000,000). Children under 15 accounted for 71.6–90.6% of annual cases, with the 5–<15-year group’s contribution rising from 12.7% (pre-COVID mean) to 27.7% in 2024. Geographic burden shifted annually with no consistently dominant region. Conclusions: Saudi Arabia’s post-pandemic rebound despite high national coverage implicates sub-population susceptibility gaps among non-national residents and school-age children, alongside importation risks from mass pilgrimage. Targeted strategies addressing demographic and geographic heterogeneity are essential to meet WHO 2030 elimination targets.

Vaccines doi: 10.3390/vaccines14050444

Authors: Carlos Fierro Daniel Brune Richard Leggett James Peterson Benjamin Lorenz Renato Calabro Calheiros Jiang Lin Anita S. Iyer Kai Wu Xin Cao Alaknanda Kondapally Sheila Marsh Shiva Kalidindi Jennifer Husson Lori Panther

Background/Objectives: No licensed vaccine against cytomegalovirus (CMV) is currently available, despite the significant risk of mother-to-infant transmission leading to serious neurodevelopmental impairment and the substantial morbidity caused by CMV infection in immunocompromised persons. We report results from a phase 2 trial of the investigational CMV mRNA vaccine mRNA-1647 and a long-term extension study (NCT04232280; NCT04975893). Methods: This randomized, observer-blind, placebo-controlled phase 2 study, conducted at 9 US sites, enrolled participants in two parts. In the first part, healthy adults aged 18–40 years were stratified by baseline CMV status into CMV-seronegative and CMV-seropositive parallel cohorts and randomized 3:1 to receive mRNA-1647 (50, 100, or 150 μg) or placebo. In the second part, healthy female participants aged 18–40 years were randomized 3:1 to receive 100 μg mRNA-1647 or placebo. In both parts, vaccine or placebo was administered at Months 0, 2, and 6. Participants completing the Primary Trial through Month 18 were eligible to enroll in the extension study, wherein safety and immunogenicity were assessed every 6 months until all participants reached Month 48 (interim analysis) and a subset had Month 54 immunogenicity samples available. Primary objectives were to assess safety and neutralizing antibody responses. Results: Solicited adverse reactions were mostly grade 1 or 2 in severity, and no notable dose-related safety trends were identified. Neutralizing antibody and antigen-specific binding IgG responses were induced in CMV-seronegative participants and boosted in CMV-seropositive participants, with durability of responses through Month 48 and up to Month 54. Conclusions: The investigational vaccine mRNA-1647 was generally well tolerated and induced durable humoral immune responses across baseline CMV serostatus, with persistence supported through Month 48 and by available Month 54 data.

Vaccines doi: 10.3390/vaccines14050443

Authors: Zheng Zhang Zhiying Xiao Xu Zhang Qian Ye Xin Zhang Wen-Song Tan

Background: Antigenic drift limits the protective efficacy of influenza vaccine. Glycosylation of hemagglutinin (HA) represents a promising immunofocusing strategy that enhances neutralizing antibody responses by masking immunodominant non-neutralizing epitopes. Methods: B-cell epitopes of influenza viruses were retrieved from the Immune Epitope Database and were mapped onto the HA structure of A/Puerto Rico/8/1934 (H1N1). Structure-guided analysis identified residues 136 and 137 as candidate sites for N-linked glycosylation (NLG). Single-site mutants (136NLG and 137NLG) were generated using reverse genetics and evaluated for stability, receptor binding, viral replication, and immunogenicity in a murine model with inactivated whole-virus vaccines. Results: Both mutants exhibited increased thermostability at 42 °C. Glycosylation reduced the HA–sialic acid affinity, resulting in decreased viral adsorption and internalization efficiency in MDCK cells, and delayed viral replication at low multiplicity of infection (MOI). In vivo, all vaccine groups provided complete protection against lethal challenge; notably, the 136NLG group exhibited reduced weight loss, indicating improved protective efficacy compared with wild-type (WT). Conclusions: Targeted glycosylation at residue 136 in the HA head domain effectively enhances the viral stability and elicits a 1.78-fold increase in hemagglutination inhibition titer (GMT) relative to the WT, thereby improving vaccine performance. These findings establish a rational and structure-based design strategy for developing more stable and effective influenza vaccines.

Vaccines doi: 10.3390/vaccines14050442

Authors: Yunjie Du Pu He Wenrui Dang Ting Zhou Yinjuan Song Xiaoping Li Yuhao Zhao Fei Li Aizhen Guo Bingdong Zhu

Background/Objectives: Several subunit vaccines for tuberculosis (TB), such as MVA85A and H4:IC31, have not demonstrated ideal protective efficacy in clinical trials, which may be attributed to their limited antigenic profile and lack of effective latency-associated antigens. In this study, we combined bioinformatics with experimental validation to screen for latency-associated antigens that have immune-protective effects. Methods: Highly expressed antigens were identified from models related to latent infections, such as hypoxia and nutritional starvation. Their physicochemical properties and immunogenicity were predicted using online tools such as Expasy-ProParam, IEBD, and VaxiJen. The immunogenicity of these antigens was then evaluated in multiple mycobacterium infection models. Finally, a systematic evaluation of the immune response and protective effects induced by the candidate antigens was performed in a mouse model using intracellular cytokine detection, mycobacterium growth inhibition assays (MGIAs), antibody-dependent cellular phagocytosis (ADCP), and a latent tuberculosis infection (LTBI) mouse model. Results: The antigen Rv2656c is highly expressed in the nutritional starvation model and demonstrates strong immunogenicity in both infected humans and cattle. Moreover, Rv2656c exerted a significant inhibitory effect against Mycobacterium tuberculosis (M. tuberculosis) and Mycobacterium avium (M. avium) infections in MGIA. The humoral immune response elicited by Rv2656c enhanced the phagocytosis and killing of Mycobacteria by macrophages in vitro. Furthermore, in a mouse model of LTBI established using the attenuated M. tuberculosis H37Ra strain, treatment with Rv2656c significantly decreased the bacterial load in the lungs of the mice. Conclusions: Latency-associated Rv2656c may serve as an immune-protective antigen, offering potential for the development of novel multi-stage antigen subunit vaccine against TB.

Vaccines doi: 10.3390/vaccines14050441

Authors: Claudia Minosse Pietro Giorgio Spezia Sara Belladonna Aurora Bettini Giulia Matusali Francesca Colavita Stefania Notari Linda Petrone Marta Tiberi Alessandro Rosario Cavasio Valentina Mazzotta Luigi Rosa Eleonora Cimini Daniele Focosi Delia Goletti Emanuele Nicastri Andrea Antinori Fabrizio Maggi

Background: Torquetenovirus (TTV) viremia is increasingly recognized as a biomarker of host immune competence. We assessed the association between baseline TTV DNA levels and immune responses to the Mpox virus (MPXV) and dengue virus (DGV) vaccines in two prospective cohorts. Methods: A total of 248 individuals were enrolled, and TTV DNA was quantified before vaccination. Humoral and cellular responses to MVA-BN (for MPXV) and QDENGA (for DGV) vaccines were measured by using serology, neutralization assays, and interferon-γ ELISpot, and correlations with TTV viremia were investigated. Results: TTV DNA was detected in 81.2% of individuals, with a significantly higher prevalence and viral loads in the Mpox-Vac group than in the DGV-Vac group. Between both groups, the only significant association observed was an inverse correlation between pre-vaccination TTV load and DGV neutralizing antibody titers in the DGV-Vac group and was limited to the subset of TTV-positive individuals; no additional correlations with antibody and T responses were identified. For the Mpox-Vac group, stratified analyses in people living with HIV (PLWH) confirmed this lack of association. Conclusions: TTV viremia does not predict vaccine immunogenicity in immunocompetent or mildly immunosuppressed individuals. These results, which derive from within-cohort analyses and do not rely on direct comparisons between heterogeneous vaccine populations, support the role of TTV as a marker of immune status along a continuum of immunosuppression, with predictive value likely confined to populations with more severe immune impairment.

Vaccines doi: 10.3390/vaccines14050440

Authors: Si Hyun Park Young Min Son

Bacterial membrane vesicles (BMVs), encompassing outer membrane vesicles (OMVs) released from Gram-negative bacteria and extracellular vesicles (EVs) released from Gram-positive bacteria, have emerged as promising vaccine platforms owing to their intrinsic immunostimulatory properties and capacity to deliver a wide range of antigens. Although conventional vaccines effectively prevent infectious diseases, their long-term efficacy is often limited by antigenic variation and reliance on a restricted number of licensed adjuvants. BMVs, as self-adjuvanting systems, enable both antigen delivery and innate immune activation. BMVs are nanoscale lipid bilayer structures enriched with pathogen-associated molecular patterns (PAMPs), facilitating their recognition and uptake by antigen-presenting cells. This leads to the activation of pattern recognition receptors and the induction of pro-inflammatory cytokines, type I interferons, and adaptive immune responses, including antibody production and Th1- and Th17-biased cellular immunity. Recent studies highlight the versatility of BMVs as vaccine platforms across bacterial, fungal, and viral infection models. BMVs induce protective immunity by promoting both systemic and mucosal immune responses, thereby reducing bacterial burden and limiting pathogen colonization across diverse infection models. These properties have supported their application in viral vaccine development, including influenza and SARS-CoV-2, with the potential to enhance mucosal immunity. Despite these advantages, challenges remain in standardization, safety, and antigen-loading efficiency. Engineered BMVs incorporating protein or mRNA antigens may further enhance antigen presentation and CD8+ T cell responses. This review summarizes the biological features, immunological mechanisms, and future potential of BMVs in vaccine development.

Vaccines doi: 10.3390/vaccines14050439

Authors: Thobelani Nompilo Majola Ntombifuthi Blose Emma Shuvai Chikovore Zinhle Mtwane Algernon Africa James Michael Burnett Maanda Mudau Noluthando Ndlovu Bontle Motloung Janine Simon-Meyer Ashnie Padarath

Background/objective: The Immunisation Agenda 2030, led by the World Health Organization, aims to ensure that people of all ages benefit from vaccination. South Africa remains committed to these goals, strengthening childhood immunisation largely through the Expanded Programme on Immunisation. However, despite progress, the number of unvaccinated and partially vaccinated children continues to rise in some urban settings. This study sought to identify barriers to childhood immunisation in selected zero-dose urban communities in Gauteng Province. Methods: A qualitative exploratory–descriptive design was used to examine factors influencing childhood immunisation. Data were collected through seven focus group discussions and fifteen key informant interviews with purposively selected caregivers, community leaders, community health workers and healthcare workers involved in routine immunisation services at public healthcare facilities across the Cities of Johannesburg, Ekurhuleni, and Tshwane. Thematic analysis was conducted using NVivo® software. Results: The study identified multiple demand-side and supply-side barriers. Demand-side barriers included limited parental knowledge, lack of trust in the government and immunisation services, religious beliefs, migration, and perceptions of caregiver substance use. Supply-side barriers involved distance to the facility, negative healthcare worker attitudes, long queues and waiting times, and frequent vaccine stock-outs. These barriers collectively contributed to missed opportunities and decreased uptake of immunisation services. Conclusions: Childhood immunisation remains a critical and cost-effective public health intervention. The findings demonstrate the complex interplay of individual and system-level factors influencing vaccine demand, uptake and persistent zero-dose status in urban Gauteng communities. Addressing these barriers requires a comprehensive approach that strengthens community trust, improves caregiver vaccine literacy, and ensures accessible, responsive, and respectful immunisation services.

Vaccines doi: 10.3390/vaccines14050438

Authors: Jessica R. Watts Jennifer L. Spencer Clinton Jeroen Pollet Rongsheng Peng Jie Tan Paul D. Ling

The authors would like to make the following corrections to this published paper [...]

Vaccines doi: 10.3390/vaccines14050437

Authors: Matteo Riccò Luca Pipitò Claudio Costantino Silvio Tafuri Chiara Noviello Marco Bottazzoli Paolo Manzoni Daniel Fiacchini Marco Falcone Pasquale Gianluca Giuri Davide Gori Antonio Cascio

Background: Workplace-related outbreaks of invasive pneumococcal disease (IPD) have been increasingly reported among shipyard workers, yet their epidemiological and clinical features remain incompletely characterized. This systematic review and meta-analysis aimed to synthesize available evidence on IPD outbreaks in shipyard settings. Methods: A systematic search of PubMed/MEDLINE, Scopus, EMBASE, and medRxiv was conducted up to March 2026. Observational studies reporting IPD outbreaks in shipyards were included. Pooled incidence rates and clinical outcomes were estimated using random-effects models, with heterogeneity assessed by I2 statistics. Risk of bias was evaluated using the Newcastle–Ottawa Scale. Results: Eight studies describing six outbreaks across four European countries (France, Norway, Northern Ireland, Finland; 2015–2025) were included, encompassing 131 cases among 35,623 workers. The pooled incidence was 368.9 cases per 100,000 workers with an attack rate of 2.36 per 1000 person-months for total cases, compared to 200.49 cases per 100,000 workers (95%CI 103.54–387.85) and 1.10 cases per 1000 person-months (95% CI 0.17–2.03) for laboratory confirmed cases, with considerable heterogeneity across studies. Most cases occurred in men (97.7%), with the median age ranging from 39 to 48 years. Hospitalizations occurred in 79.1% of cases, intensive care unit admission in 13.7%, and the case fatality ratio was 0.8%. Serotype 4 accounted for 67.2% of characterized isolates. Occupational exposures and shared accommodation may have contributed to transmission, although this could not be formally assessed. Conclusions: IPD outbreaks in shipyard settings are characterized by high incidence but relatively favorable outcomes, likely reflecting workforce demographics. However, considerable heterogeneity and methodological limitations across studies constrain the interpretation of pooled estimates. Preventive strategies, including vaccination and workplace-targeted interventions, should be considered as plausible public health measures, with a proactive role for occupational health services.

Vaccines doi: 10.3390/vaccines14050436

Authors: Quexun Cai Qianli Yang Kangrui Zhang Zhengyue Fei Ruochen Zhao Tao Lu Kecheng Xu Zhenyi Wang Peihua Lu

Background: Lung cancer is the top cause of cancer-related mortality globally, and chemo-immunotherapy is a core therapeutic strategy for it. The novel bacterial composite vaccine (Neo-BCV) we developed previously can activate anti-tumor immunity. This study explored its synergistic anti-tumor effect with cisplatin (CDDP), along with the underlying immunomodulatory mechanisms and molecular regulatory networks. Methods: A murine Lewis lung cancer (LLC) model was established to evaluate the efficacy of the combination therapy. Flow cytometry and multiplex cytokine assay were used to detect immune cell subsets and functional molecules in the spleen, serum and tumor tissues. RNA-sequencing (RNA-seq) was used to elucidate the molecular regulatory networks following the combination therapy in the tumor tissues. Body weight, blood indexes, serum biochemistry and H&E staining were monitored to verify biosafety. Results: Neo-BCV combined with CDDP achieved an 87.77% tumor growth inhibition rate, showing the most significant anti-tumor effect. The combination promoted DC maturation, enhanced effector immune cell infiltration, reduced immunosuppressive cells, upregulated Th1-type cytokines and downregulated CD8+ T cell surface PD-1. RNA-seq confirmed enrichment of multiple immune effector pathways, supporting tumor immune microenvironment remodeling. The combination alleviated CDDP-induced weight loss, had no obvious adverse effects on physiological indicators, and exhibited good biosafety. Conclusions: Neo-BCV combined with CDDP achieves enhanced anti-tumor efficacy and favorable biosafety in murine lung cancer models by regulating immune cell subsets and activating immune-related molecular pathways, providing a solid preclinical basis for its clinical translation in lung cancer treatment.

Vaccines doi: 10.3390/vaccines14050435

Authors: Hye-Mi Lee

Feline infectious peritonitis virus (FIPV) remains one of the most challenging viral diseases in veterinary medicine, largely owing to the absence of a consistently effective and safe vaccine. Despite widespread feline coronavirus infection, only a subset of infected cats progresses to feline infectious peritonitis, indicating that host immune responses are key determinants of disease outcomes. Accumulating evidence indicates that disease severity is driven not only by viral replication but also by macrophage- and monocyte-centered immune signaling, leading to excessive inflammation and systemic immunopathology in the host. Previous vaccine approaches against FIPV have failed to provide consistent protection and, in some cases, have been associated with enhanced disease. These outcomes suggest that vaccine-induced immune responses that recapitulate pathogenic signaling patterns may exacerbate disease rather than confer protection. In this review, we discuss the current knowledge of immune cell signaling pathways implicated in FIPV infection, including innate sensing through Toll-like receptors, downstream mitogen-activated protein kinases and NF-κB signaling, cytokine production profiles, Fc receptor-associated processes, and intracellular pathways such as autophagy, and how these mechanisms shape vaccine-induced immunity. By integrating insights from immune signaling kinetics, antibody functionality, adjuvant-driven pathway engagement, and platform-specific immune signatures, this review emphasizes the need to reframe FIPV vaccine development strategies that actively shape host immune responses. Rather than maximizing immunogenicity, successful vaccine design is likely to depend on limiting sustained macrophage activation and pro-inflammatory cytokine amplification while supporting antiviral immune functions, thereby reducing the risk of antibody-dependent enhancement and immunopathology. Beyond feline diseases, these considerations provide broader lessons for vaccine design in settings where immune-mediated pathology contributes to disease severity.

Vaccines doi: 10.3390/vaccines14050434

Authors: Sonia Moretti Ivan Schietroma

We are pleased to present this closing editorial for the Special Issue “Vaccines and Vaccination: HIV, Hepatitis Viruses and HPV”, which we had the privilege of coordinating [...]

Vaccines doi: 10.3390/vaccines14050433

Authors: Sergio Loayza Bertha Capistrán Marcela Contreras Martha Velandia Daniel Salas

The authors would like to make the following correction to this published paper [...]

Vaccines doi: 10.3390/vaccines14050432

Authors: Joyce Omondi Robert Ambogo Candy Ochieng Marwa Farag George Mutwiri

Background: The COVID-19 pandemic caused disruptions in HPV vaccination and may have severely undermined global cervical cancer prevention, posing long-term risks to controlling cervical cancer and other HPV-related diseases. Objective: We conducted a scoping review to map and synthesize available evidence on how the COVID-19 pandemic has affected human papillomavirus (HPV) vaccination programs in low- and middle-income countries (LMICs) focusing on changes in vaccine delivery and coverage, determinants of uptake, economic and programmatic consequences and vaccine hesitancy. Methods: Inclusion criteria were limited to studies published in the English language between January 2020 to May 2025, and followed JBI and Arksey & O’Malley’s scoping review guidelines. The review proceeded through three stages: database searches, gray literature and citation tracking and used a PRISMA-ScR checklist to guide narrative and tabular synthesis. Results: A total of 1063 records, 57 studies were included in the final analysis, and these were spread out across 37 low- and middle-income countries (LMICs) mainly in Africa, Asia, and Latin America. Our analysis revealed that HPV vaccination coverage declined substantially during the COVID-19 pandemic, with reductions of up to 90% reported across the included studies, in the context of school closures, workforce redeployment, and supply-chain disruptions. Recovery efforts also faced major barriers including vaccine hesitancy, misinformation about COVID-19 vaccines, and travel restrictions. Strategies like digital tools, mobile clinics, and community health workers showed promise alongside integrated school- and facility-based approaches, although there is limited evidence on cost-effectiveness and long-term sustainability of these strategies. Conclusions: HPV vaccination in LMICs was significantly disrupted by the COVID-19 pandemic due to unreliable vaccine supply chains, health-worker shortages, and challenges tied to school-based vaccine delivery. Although recovery methods show potential, longer observation periods are needed to determine their full effectiveness.

Vaccines doi: 10.3390/vaccines14050431

Authors: Matthew R. Boyce Rebecca Katz

Background/Objectives: In a context characterized by persistent vaccine hesitancy, shifting mandates, and stagnating immunization coverage rates, novel policy tools may be required to bolster immunization coverage in the United States. We conducted a national survey to characterize public support for a new tax policy that would require parents to prove that their children are age-appropriately immunized against polio to be eligible for the federal child tax credit. Methods: The survey was conducted in November 2025. Respondents were asked to provide demographic information and use a Likert-scale to indicate their support for the proposed policy. Chi-squared tests and ordinal logistic regression models were used to compare support for the proposed policy across subpopulations. Results: 980 individuals were included in the analysis. 55.8% of respondents supported adding age-appropriate polio immunization to the child tax credit eligibility criteria. 20.9% of respondents opposed the policy proposal. Relative levels of support for the policy differed according to respondent gender, age, 2024 presidential election behavior, and geographic region. However, support did not differ significantly according to race, ethnicity, educational attainment, income, or partisanship. Conclusions: Results show that most survey respondents would support a policy that would add polio immunization status to the eligibility criteria for the federal child tax credit. Further, support did not differ across key demographic and political subgroups. Larger surveys should validate these findings and investigate support for adding additional vaccines to the eligibility criteria.

Vaccines doi: 10.3390/vaccines14050430

Authors: Clairissa A. Hansen Shawn Rast Jill K. Thompson Haiping Hao Daniel Jupiter Stephen Higgs Nigel Bourne Alan D. T. Barrett

Background/Objectives: The envelope (E) protein of orthoflaviviruses contains antigenic sites that are composed of one or more epitopes, which can vary in antigenic specificity, including between viral species, strains, and even substrains. Monoclonal antibodies (mAbs) that bind these epitopes vary in functionality based on their specificity. This makes mAbs useful to study the differences in phenotypes between strains of viruses, such as the wild type (WT) and live attenuated vaccine strains of yellow fever virus (YFV). mAb 2D12 was raised against the 17D-204 YFV vaccine substrain virus (YF VAX®) by Schlesinger et al. in 1983. However, it only neutralizes Asibi WT virus, not the 17D-204 vaccine substrain virus. Results: We confirmed these results and demonstrated that mAb 2D12 fails to neutralize all 17D vaccine substrains (17D-204, 17DD, and 17D-213), indicating that the minor differences between these virus substrains do not affect the epitope or functionality of mAb 2D12. In addition, mAb 2D12 was found to neutralize WT strain of French viscerotropic virus (FVV), with statistically indistinguishable neutralization from the WT strain Asibi. All but one of the live attenuated French neurotropic vaccine (FNV) derivative viruses had significantly lower neutralization than WT strains Asibi and FVV. FVV, Asibi, 17D, and FNV have many amino acid differences in the membrane (M) and E proteins. It is unclear which of them contributes to this differential neutralization. However, FNV and 17D have common amino acid substitutions from WT FVV and Asibi at positions M-36 and E-331, suggesting that one or both of these residues may contribute to the 2D12 epitope. Conclusions: Overall, mAb 2D12 is a valuable tool to distinguish WT virulent strains of YFV from live attenuated vaccine strains.

Vaccines doi: 10.3390/vaccines14050429

Authors: Daliana Lobo Torres Zahid Ahmad Butt

Background: Booster vaccine hesitancy poses a challenge to sustained COVID-19 immunization even among individuals who accepted primary vaccination. This study examined associated factors and patterns of change in vaccine attitudes among university students in Ontario, Canada. Methods: A cross-sectional survey dataset was analyzed using validated psychometric scales to measure hesitancy toward primary and booster COVID-19 vaccination. Changes in hesitancy were operationalized as the continuous difference between booster and primary scores (ΔVH). Gradient Boosting and XGBoost regression models were fitted to estimate ΔVH from demographic characteristics (age, gender, socioeconomic status), vaccination history, and attitudinal constructs including complacency, confidence in vaccine safety, and perceived necessity of vaccination. Predictor contributions were assessed using SHapley Additive exPlanations, and Gaussian Mixture Modeling was employed to identify latent profiles among students with increased hesitancy. Results: A substantial proportion of students demonstrated higher hesitancy toward booster doses. Attitudinal factors, particularly complacency and safety perceptions, were the most influential predictors of increased hesitancy, whereas sociodemographic characteristics showed limited influence. Three distinct profiles of booster hesitancy were identified, reflecting heterogeneous patterns of vaccine attitudes and behaviors. Conclusions: These findings suggest that booster hesitancy in the study population is primarily associated with modifiable perceptions and can be effectively characterized using machine learning approaches that may inform targeted public health communication strategies.

Vaccines doi: 10.3390/vaccines14050428

Authors: Yingying Zhou Wenqiang Wang Yun Kuang Qiang Hu Lin Shen Qiangming Xie Zhi Xie

Background: Mpox vaccination is an important prevention strategy for men who have sex with men (MSM), yet responses to vaccination may not be adequately captured by a simple willing-versus-unwilling framing. We examined correlates of vaccination willingness and heterogeneity within the delayed/refused responses subgroup in Changsha, China. Methods: A cross-sectional survey was conducted using respondent-driven sampling (RDS). Vaccination willingness was classified as immediate willingness versus delayed/refused responses. Analyses included cluster-robust logistic regression, RDS-weighted regression, generalized estimating equations, and a recruiter-linked network-lag model. Among respondents with delayed/refused responses, concern profiles were explored using unsupervised clustering of standardized concern items. Results: Among 405 recruited MSM without a self-reported mpox infection history, immediate willingness and delayed/refused responses were nearly equally distributed, indicating that lack of immediate willingness was common. Across primary models, ever use of pre-exposure prophylaxis (PrEP) and higher mpox-related information exposure frequency were the most consistent correlates of immediate willingness versus delayed/refused responses, whereas basic sociodemographic variables showed little evidence of independent association. Within the delayed/refused group, three partially overlapping patterns emerged: broadly elevated cross-domain concern, low-concern delay with few strongly endorsed barriers, and more selective safety- and burden-related concerns. These findings suggest that a lack of immediate willingness may arise through different psychosocial pathways rather than a single common mechanism. Conclusions: Mpox vaccination willingness among MSM in Changsha appeared to be shaped more by prevention-related behaviors and psychosocial factors than by basic sociodemographic profiles alone. Vaccination strategies may benefit from cross-topic sexual-health communication, integrated prevention efforts, and subgroup-sensitive approaches to delayed or refused willingness.

Vaccines doi: 10.3390/vaccines14050427

Authors: Paola Dall‘Ara Lucia Tamanza Federico Alghisi Davide Raccagni Alice Garegnani Joel Filipe

Background/Objectives: International guidelines advocate for personalized vaccination protocols using point-of-care (POC) antibody titration to identify dogs requiring boosters for CPV-2, CDV, and CAdV-1. As traditional venipuncture can be challenging in specific patients, this study evaluate the clinical agreement of a novel minimally invasive capillary blood sampling technique (ear-prick) for core vaccine antibody titration. Methods: Paired blood samples were collected from 55 healthy dogs using venipuncture and an ear-prick technique with a portable lancet. Antibody titers were determined using a semi-quantitative POC kit (VacciCheck® Canine). The procedure was optimized comparing 28G and 21G lancets, with the latter used in 43 dogs to ensure adequate blood flow. Comprehensive statistical methods evaluated the correlation and agreement between the two sampling techniques. Results: Statistical analysis showed no significant differences between sampling methods (p > 0.05). In the optimized group (21G lancet), full match rates reached 81.4% for CPV-2, 76.8% for CDV, and 74.4% for CAdV-1. Clinical concordance was exceptionally high: 95.3% for CPV-2, 90.7% for CDV, and 100% for CAdV-1. Statistical analysis confirmed perfect agreement (1.00) for CPV-2 and CAdV-1, and moderate agreement (0.48) for CDV. Conclusions: The ear-prick technique using a 21G lancet is a reliable, minimally invasive alternative to venipuncture for antibody titration. This method simplifies clinical procedures and facilitates personalized immunization monitoring. Given the minimal blood volume required, it represents a versatile approach for evaluating immune status and protection levels to core vaccines in diverse settings, including pediatric and shelter medicine.

Vaccines doi: 10.3390/vaccines14050426

Authors: Adi Lahat Kassem Sharif

Vaccination remains one of the most effective public health interventions for preventing infectious diseases, reducing morbidity, mortality, and healthcare burden worldwide [...]

Vaccines doi: 10.3390/vaccines14050425

Authors: Lei Zhou Yunkang Zhao Hongjie Wei Kang Fang Huimin Qu Yanshu Ke Jia Rui Dayan Wang Tianmu Chen Liming Li

Background: China‘s influenza vaccination coverage remains at a low rate, with significant regional socioeconomic disparities, lacking targeted distribution strategies and achievable coverage targets. This study aims to provide scientific evidence for formulating differentiated and feasible vaccination strategies across Chinese provinces based on regional economic gradients. Methods: We employed the Susceptible-Vaccinated-Exposed-Asymptomatic-Infectious-Critical-Fatal-Recovered/Removed (SVEAICFR) model to simulate various vaccination strategies, analyzing the reduction in disease burden and vaccine dose requirements across underdeveloped, developing, and developed regions. The optimal strategy and achievable coverage targets were subsequently determined. Results: The 31 provinces were clustered into three categories based on economic levels, showing significant spatiotemporal differences in epidemics (Kruskal–Wallis test, all p < 0.001). Developed regions showed the earliest onset and highest peaks (influenza-like illness positive (ILI+) index ≈ 12–13, Baidu Influenza Search Index (BISI) ≈ 310,000). Developing regions exhibited moderate lagging by 1–2 weeks, while underdeveloped regions had the lowest peaks (ILI+ 3–4) and longer epidemic cycles. During the 2023–2024 influenza season, the national predicted vaccination rate was only 2.89% with marked regional disparities. Baseline incidence, severity, and mortality rates were 13,374.93, 49.52, and 8.37 cases per 100,000 population, respectively. Modeling indicates that increasing influenza vaccination coverage rates for populations aged <18 and ≥65 to a theoretical threshold (39.73% of the total population) before the season could reduce incidence, severity, and mortality rate by 99.26%,99.42%, and 99.46%, respectively. Conclusions: Influenza prevalence in China exhibits significant regional heterogeneity, necessitating differentiated measures based on regional economic gradients. Regional support mechanisms should be implemented to promote equitable vaccine distribution. Priority vaccination for high-risk populations (aged <18 and ≥65), to reach a 40% theoretical national coverage target, is recommended via realistic implementation pathways to minimize the disease burden of influenza.

Vaccines doi: 10.3390/vaccines14050424

Authors: Heather R. Hensler Tianyi Lu Yoonyoung Park Machaon Bonafede Isabelle Winer Christopher Adams Keya Joshi Amanda Wilson

Background/Objectives: We still do not clearly know whether COVID-19 continues to impose a greater clinical burden than influenza in the “post-pandemic” era. Our study quantified and compared monthly COVID-19 and influenza hospitalization incidence among adult subgroups from October 2022 through December 2024. We assessed vaccine coverage trends and examined vaccination status among those hospitalized. Methods: Using the Veradigm linked claims and electronic health record dataset, we conducted a non-interventional, retrospective cohort study; three monthly cohorts included individuals aged 65+, high-risk (HR) adults (defined as adults 18+ with HR conditions and/or aged 65+), and adults aged 50–64 years who were enrolled with both medical and pharmacy coverage. We estimated monthly cumulative incidence of COVID-19 and influenza-related hospitalizations, vaccination coverage rates, and the proportion of hospitalized individuals who had received yearly updated vaccines. Results: COVID-19 hospitalizations consistently exceeded those of influenza across months and populations. Among adults aged 65+, COVID-19 hospitalization rates were 2–3 times higher than influenza in winter and 20–30 times higher during off-season months, with similar trends observed in high risk adults. COVID-19 incidence surged in summer, while influenza remained seasonally confined. Vaccination coverage for influenza peaked near 50% annually; COVID-19 coverage was lower, peaking at ~26% by December each year. Most hospitalizations occurred among unvaccinated individuals, particularly for COVID-19. Conclusions: COVID-19 continues to impose a substantial, year-round burden, particularly in older and high-risk adults, exceeding that of influenza. The high proportion of unvaccinated hospitalizations highlight a critical gap in prevention efforts and underscore the need for improved public health messaging and vaccine adoption.

Vaccines doi: 10.3390/vaccines14050423

Authors: Barbara de Oliveira Baptista Isabela Ferreira Soares Hugo Amorim dos Santos de Souza Jenifer Peixoto de Barros Evelyn Kety Pratt Riccio Rodrigo Medeiros Martorano Rodrigo Nunes Rodrigues-da-Silva Linda Eva Amoah Susheel Kumar Singh Michael Theisen Josué da Costa Lima-Junior Paulo Renato Rivas Totino Cláudio Tadeu Daniel-Ribeiro Lilian Rose Pratt-Riccio

Background/Objectives: The GMZ2.6c malaria vaccine candidate is a multi-stage P. falciparum chimeric protein that contains a fragment of the sexual stage Pfs48/45-6c protein genetically fused to GMZ2, which is an asexual stage vaccine construct consisting of conserved domains of Glutamate-Rich Protein (GLURP) and Merozoite Surface Protein-3 (MSP-3). Previous studies showed that GMZ2.6c is widely recognized by antibodies from individuals living in endemic areas of Brazil and that levels of anti-GMZ2.6c increase with malaria exposure and may contribute to immunity against the parasite. As cell-mediated responses are crucial for parasite control and protection, identifying antigens that elicit antigen-specific T cell recall in naturally exposed populations is the key to vaccine development. This study aimed to evaluate the cellular immune response against GMZ2.6c and its components (MSP-3, GLURP, and Pfs48/45) and to identify promiscuous T cell epitopes in individuals exposed to malaria in the Brazilian Amazon, considering the impact of active P. falciparum infection on antigen-specific T cell recall. Methods: This study was carried out using peripheral blood mononuclear cells (PBMCs) from individuals with active P. falciparum infection (PFI) and non-infected individuals exposed to malaria (NI) from Cruzeiro do Sul and Mâncio Lima, Acre State, and Guajará, Amazonas State. The PBMCs were stimulated with GMZ2.6c and its components, and cellular activation, CD4+ and CD8+ memory T cell subsets, and cytokine production were evaluated by flow cytometry. IFN-γ-secreting T cells were quantified by ELISpot using predicted T cell epitopes. Results: The individuals infected by P. falciparum displayed more CD8+ T cell activation in response to MSP-3 and Pfs48/45 and an increase in CD4+ TCM cells and a reduction in CD4+ TEM cells following stimulation with Pfs48/45 and GMZ2.6c. The PBMCs from both groups showed elevated production of IL-6 and TNF after stimulation with GMZ2.6c, MSP-3, and Pfs48/45, but only the non-infected individuals had high levels of IL-10. T cell epitope prediction identified sequences within MSP-3, GLURP, and Pfs48/45 that elicited IFN-γ responses in both the non-infected and P. falciparum-infected individuals. Conclusions: Individuals exhibit cellular immune responses to MSP-3 and Pfs48/45 that are recalled following GMZ2.6c stimulation. P. falciparum infection may modulate immune response, inducing a prominent pro-inflammatory response. Conversely, in the absence of the parasite, the individuals displayed balanced Th1/Th2 cytokine production. Several promiscuous T cell epitopes were able to recall IFN-γ responses. Further studies are needed to fully ascertain the potential of GMZ2.6c as a protective candidate vaccine against malaria.

Vaccines doi: 10.3390/vaccines14050422

Authors: Holly B. Fontenot Siobhan Coad Erica J. Liebermann Erika L. Thompson Emma Collo Tiffannie Chang Melanie Kornides Gregory Zimet

Background/Objective: The objective of this study was to explore parental preferences for the age of HPV vaccination (9–12) and the rationales for these preferences. Methods: Four online text-based focus groups were conducted with a national sample of 43 parents who have at least one child aged 9–10 years. Participants discussed preferred age for HPV vaccination and how it relates to the routine adolescent vaccine schedule in the United States (US). Content analysis was utilized to identify emergent themes. Results: Three themes surrounding parents’ motivating factors related to HPV-vaccination schedule preferences emerged from the analysis of the focus group discussions: (1) a belief that age 9 is too young versus a belief in early protection, (2) the number of shots administered per visit (a desire to spread shots out or group together), and (3) the parent follows their health care provider’s recommendations. Conclusions: This qualitative study of parental preferences regarding HPV vaccination age and how it relates to the routine adolescent vaccine schedule reveals mixed parental decision-making and rationales for vaccine acceptance and at which age. Given the dynamic vaccine policy landscape in the US, it is essential for providers to understand parental perspectives and motivating factors related to vaccine decision-making and integrate these drivers into clinical practice to best support families and public health at large.

Vaccines doi: 10.3390/vaccines14050421

Authors: Byeol-Hee Cho Ju Kim Yong-Suk Jang

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects host cells through the interaction between the spike protein receptor-binding domain (RBD) and the human angiotensin-converting enzyme 2 (hACE2) receptor, which is expressed on epithelial cells in various tissues, including the respiratory tract. Therefore, mucosal immunity in the respiratory tract plays a key role in protection against viral infection. Previously, we demonstrated that intranasal administration of antigens (Ags) conjugated with the M cell-targeting peptide Co4B enhances both mucosal and systemic immune responses. That conjugation with human β-defensin 2 (HBD2) increases neutralizing antibody (Ab) responses. Methods: A recombinant antigen conjugate incorporating both Co4B and HBD2 was designed to enhance immunogenicity. Its immunogenicity was evaluated in mice following intranasal immunization. Antigen-specific antibody responses were measured in serum and bronchoalveolar lavage fluid. T-cell responses were evaluated in lungs and spleens. Protective efficacy was assessed using SARS-CoV-2-susceptible hACE2 knock-in mice. Results: Ag-specific Ab levels increased in both serum and bronchoalveolar lavage fluid of mice immunized intranasally with the conjugate. Especially, T-cell responses were significantly enhanced in the lungs and spleens of immunized hACE2 knock-in mice. In challenge experiments, intranasal administration of the conjugate reduced viral load. Moreover, Siglec F was identified as a potential receptor for Co4B, a previously uncharacterized M cell-targeting ligand. Conclusions: A recombinant viral Ag containing Co4B and HBD2 induces virus-specific humoral and cellular immune responses. Although further optimization of the vaccine formulation and administration strategy is needed, this conjugate shows potential as a platform for improving mucosal and systemic immunity.