Vaccines

18 pages, 1002 KB

Open AccessReview

Access to Vaccines Among Asylum Seekers, Refugees, and Undocumented Migrants Across the Migratory Cycle in the European Union, European Economic Area, Switzerland and the United Kingdom: A Scoping Review

by Saleh Aljadeeah, Anil Babu Payedimarri, Carine Dochez, Karina Kielmann, Veronika J. Wirtz, Sally Hargreaves and Raffaella Ravinetto

Vaccines 2026, 14(6), 551; https://doi.org/10.3390/vaccines14060551 - 22 Jun 2026

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Abstract

Introduction: Inequities in access to medicines persist for asylum seekers, refugees, and undocumented migrants in Europe. For vaccines, access gaps not only exist for these groups in childhood routine immunization, but also for life-course and catch-up vaccinations. As part of a broader [...] Read more.

Introduction: Inequities in access to medicines persist for asylum seekers, refugees, and undocumented migrants in Europe. For vaccines, access gaps not only exist for these groups in childhood routine immunization, but also for life-course and catch-up vaccinations. As part of a broader project examining access to medicines and vaccines for migrants across all stages of the migration cycle, this scoping review synthesizes evidence on the determinants of access to vaccines. Methods: We conducted a scoping review across PubMed, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Cochrane Database of Systematic Reviews, Scopus, and grey literature sources, covering the period 2000–2024. Sources were eligible if they addressed access to vaccines among migrants. We examined access to vaccines along the life course, and across phases of the migratory cycle, including departure, transit, reception and settlement, and return or deportation. Results: A total of 47 research studies and grey literature reports were included. Most studies focused on migrants in reception and settlement (destination) settings, with only twelve sources addressing other phases of the migratory cycle. Across European countries, migrants were frequently reported to have lower uptake of routine vaccines (e.g., measles–mumps–rubella (MMR), polio, diphtheria–tetanus–pertussis (DTP), and human papillomavirus (HPV)) and COVID-19 vaccines than host populations. The most frequently reported barriers were related to migrants’ legal status, administrative requirements, and lack of documentation, alongside poor affordability of vaccination, limited awareness of their rights, and mistrust in the health system. Conclusions: Health systems need to adopt innovative approaches to expand vaccine access for migrant populations. Further, protecting confidentiality is essential for building trust and reducing ethical and legal risks. Flexible and coordinated vaccination strategies are required to address migrants’ mobility across the different migration stages and settings. Our findings appeal for sustained improvements in access to vaccines among migrants in Europe, contingent on strong policy commitments to equity, data protection, and the adoption of life-course and catch-up vaccination strategies. Full article

(This article belongs to the Special Issue The Role of Vaccination on Public Health and Epidemiology)

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15 pages, 284 KB

Open AccessReview

Advances in Detection Methods for Human Respiratory Syncytial Virus Neutralizing Antibodies

by Qi Shen, Jing Gai and Yanqiu Zhou

Vaccines 2026, 14(6), 550; https://doi.org/10.3390/vaccines14060550 - 22 Jun 2026

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Abstract

Human respiratory syncytial virus (HRSV) is a major cause of severe lower respiratory tract infections in infants, young children, and older adults worldwide. With the approval of nirsevimab and HRSV vaccines, accurate measurement of neutralizing antibody levels has become essential for vaccine evaluation, [...] Read more.

Human respiratory syncytial virus (HRSV) is a major cause of severe lower respiratory tract infections in infants, young children, and older adults worldwide. With the approval of nirsevimab and HRSV vaccines, accurate measurement of neutralizing antibody levels has become essential for vaccine evaluation, immunization strategy design, and seroepidemiology. The plaque reduction neutralization test (PRNT) remains the gold standard, but it is slow, low-throughput, and requires high biosafety. In recent years, newer methods including focus reduction neutralization testing (FRNT), pseudovirus neutralization testing (PNT), and fluorescent/luminescent reporter virus systems (RVSs) have improved speed and throughput while maintaining high specificity. This review summarizes the principles, performance, applications, and standardization challenges of these assays, offering methodological guidance for HRSV research and prevention in China. Full article

(This article belongs to the Collection Research on Monoclonal Antibodies and Antibody Engineering)

11 pages, 421 KB

Open AccessArticle

Insights from 25 Years of Measles and Measles–Rubella Vaccination Campaigns in the WHO African Region (2001–2025)

by Balcha Girma Masresha, Goitom Gebremedhin Weldegebriel, Emmaculate Jepkorir Lebo, Sarah Wanyoike, Ado Mpia Bwaka and Yolande Vuo-Masembe

Vaccines 2026, 14(6), 549; https://doi.org/10.3390/vaccines14060549 - 22 Jun 2026

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Abstract

Introduction: The WHO African Region is working to eliminate measles and rubella in 80% of countries by 2030. In countries with sub-optimal routine immunization coverage, periodic supplemental Immunization Activities (SIAs) are implemented to boost childhood immunity against measles and rubella. Methods: We reviewed [...] Read more.

Introduction: The WHO African Region is working to eliminate measles and rubella in 80% of countries by 2030. In countries with sub-optimal routine immunization coverage, periodic supplemental Immunization Activities (SIAs) are implemented to boost childhood immunity against measles and rubella. Methods: We reviewed the SIA technical reports and reports from post-campaign surveys shared by countries with the WHO Regional Office for Africa, and we analyzed the coverage data from preventive measles campaigns implemented during the years 2001–2025. Results: A total of 326 preventive measles/measles–rubella SIAs were implemented across 44 countries in the years 2001–2025, providing more than 1.5 billion doses of vaccine to eligible children according to the type and scale of the campaigns. Four fifths (82%) of the SIAs were nationwide exercises, and all of the SIAs were implemented as non-selective vaccination campaigns targeting all eligible children irrespective of past vaccination history, with the exception of four SIAs. The 95% administrative SIA coverage target at national level was met in 209 SIAs (64.7%). At district level, 11 of 164 SIAs had 100% of districts attaining 95% administrative coverage. Only 94 SIAs (29%) were followed by post-campaign coverage survey, and only 18 (19%) of these attained coverage of 95% or more by survey. Nearly two thirds (62%) of the 272 SIAs implemented during 2006–2025 had at least one additional intervention included with the measles/MR vaccination. Discussion: Measles and MR vaccination campaigns have served as excellent opportunities for providing integrated child survival interventions in the African Region. While two thirds of the SIAs met the national administrative coverage target, district-level coverage targets were not met in the majority of the SIAs, and only one fifth of the SIAs met the national-level survey coverage targets. Moreover, discrepancies were noted between administrative and survey coverage results, possibly due to inaccuracies in the reporting of the number of doses administered and/or reliance on inaccurate denominators. For optimal impact, SIAs need to adequately reach unreached populations. Conclusions: In view of the documented sub-optimal coverage, countries should provide strong leadership and ownership of the measles elimination strategies for the attainment of the SIA coverage targets as well as the overall measles and rubella elimination goal. There is an urgent need for improved tools to identify unvaccinated children, high-risk populations, and innovative strategies to reach them. All countries implementing SIAs should also include systematic monitoring of zero-dose children, and conduct post-campaign coverage surveys in a timely manner. Full article

(This article belongs to the Section Vaccines and Public Health)

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13 pages, 291 KB

Open AccessArticle

Post-Marketing Safety Surveillance of Influenza Vaccines in Anhui Province, China, 2016–2025

by Fanya Meng, Sicheng Wei, Binbing Wang, Xianwei Luo and Jiabing Wu

Vaccines 2026, 14(6), 548; https://doi.org/10.3390/vaccines14060548 - 21 Jun 2026

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Abstract

Background: China’s influenza vaccine (InfV) has undergone multiple iterations and numerous technological breakthroughs, providing tremendous impetus and solid support for the development of China’s health sector. As the number of vaccinated individuals continues to rise, the importance of ongoing surveillance and evaluation [...] Read more.

Background: China’s influenza vaccine (InfV) has undergone multiple iterations and numerous technological breakthroughs, providing tremendous impetus and solid support for the development of China’s health sector. As the number of vaccinated individuals continues to rise, the importance of ongoing surveillance and evaluation of vaccine safety has become increasingly prominent, forming part of efforts to maintain public trust in the national immunization program and ensure its sustainability. Methods: From 2016 to 2025, data on suspected adverse events following immunization (AEFIs) related to InfV administration were extracted from the Chinese National Immunization Information System (CNIIS). Data on InfV vaccination doses were obtained from the Anhui Provincial Immunization Information Management System. A descriptive statistical method was used to analyze the distribution characteristics of AEFIs, and the chi-square test was applied to evaluate differences in reporting rates. Results: Between 2016 and 2025, a total of 4026 AEFI reports related to InfV were monitored through the CNIIS. The overall reporting rate was 34.40 per 100,000 doses. Specifically, common adverse reactions and rare adverse reactions accounted for 95.88% (3860 cases) and 3.38% (136 cases), with reporting rates of 32.98 per 100,000 doses and 1.16 per 100,000 doses, respectively. Among common adverse reactions, the reporting rates of fever (axillary temperature ≥ 38.6 °C), local redness and swelling at the injection site (diameter > 5.0 cm), and local induration (diameter > 5.0 cm) were 9.62 per 100,000 doses, 1.96 per 100,000 doses, and 1.20 per 100,000 doses, respectively. Among rare adverse reactions, the reporting rates of allergic rash, angioedema, anaphylactic shock, febrile convulsions, anaphylactoid purpura, thrombocytopenic purpura, epilepsy, Guillain–Barré syndrome, and aseptic abscess were 0.98, 0.05, 0.03, 0.03, 0.02, 0.02, 0.01, 0.01, and 0.01 per 100,000 doses, respectively. No cases were reported for subunit inactivated influenza vaccine (IIV, Subunit). Statistically significant differences were observed in the reporting rates of allergic rash across different types of InfV (χ² = 36.83, p < 0.05), with trivalent inactivated influenza vaccine (IIV3, Split) and trivalent live attenuated influenza virus vaccine (LAIV3) showing the highest reporting rates. Most adverse events following vaccination occurred within 24 h after inoculation. Conclusions: From 2016 to 2025, the overall reporting rate of AEFIs after InfV administration in Anhui Province was within an acceptable range. Common adverse reactions were common, while rare adverse reactions were few, mainly consisting of allergic reactions. These results indicate that InfV has a favorable safety profile, and continuous strengthening of AEFI surveillance for InfV and improvement of surveillance quality are warranted. Full article

(This article belongs to the Special Issue Vaccines Against Influenza and Other Respiratory Virus Infections)

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10 pages, 503 KB

Open AccessArticle

Characteristics of Hypotonic–Hyporesponsive Episodes (HHEs) Following Childhood Vaccination: A 13-Year Analysis of Spontaneous Reports to the Dutch Pharmacovigilance Centre Lareb

by Sanne Boetzkes, Leontine van Balveren and Florence van Hunsel

Vaccines 2026, 14(6), 547; https://doi.org/10.3390/vaccines14060547 - 20 Jun 2026

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Abstract

Background: Hypotonic–hyporesponsive episode (HHE) is a recognised adverse event following immunisation (AEFI) in infants, characterised by sudden hypotonia, hyporesponsiveness, and pallor or cyanosis. Although considered benign, its abrupt and often dramatic presentation often leads to acute medical evaluation. Contemporary data on HHE are [...] Read more.

Background: Hypotonic–hyporesponsive episode (HHE) is a recognised adverse event following immunisation (AEFI) in infants, characterised by sudden hypotonia, hyporesponsiveness, and pallor or cyanosis. Although considered benign, its abrupt and often dramatic presentation often leads to acute medical evaluation. Contemporary data on HHE are limited, and awareness among healthcare professionals needs attention. Methods: We conducted a retrospective analysis of all spontaneous reports of HHE submitted to the national pharmacovigilance centre Lareb between 1 January 2012 and 22 July 2025. Cases were included only when meeting Brighton Collaboration (BC) Level 1 criteria, requiring clear documentation of hypotonia, hyporesponsiveness, and pallor or cyanosis in children younger than 24 months. Demographic and clinical characteristics, vaccine combinations, latency, duration, seriousness, and medical care utilisation were described. Results: A total of 294 Level 1 HHE cases were identified. Most episodes followed combinations of hexavalent vaccines with pneumococcal conjugate vaccines. The median age at onset was 9 weeks, with slightly more reports involving boys. The median latency to onset was 5 h (range 4–8 h), and the median episode duration was 10 min (range 3–30 min), aligning with the historical literature. All children recovered fully, and no long-term sequelae were reported. Although HHE is clinically benign, 27% of cases were classified as serious, primarily due to hospital admission. Among non-serious cases, one third involved medical assessment or emergency services. Healthcare professionals submitted 44% of reports, notably community child health physicians. Conclusions: Contemporary Dutch pharmacovigilance data confirm that the clinical characteristics of HHE remain highly consistent with long-standig evidence. Despite its benign and self-limiting nature, HHE frequently triggers substantial medical care consumption. Improved awareness of the typical presentation, course, and prognosis, supported by the Brighton Collaboration criteria, may help clinicians recognise HHE more readily, reduce unnecessary medical consumption, and provide reassurance to caregivers. Full article

(This article belongs to the Special Issue The Changing Epidemiology of Vaccine-Preventable Diseases)

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27 pages, 3978 KB

Open AccessArticle

Faith, Science, and Choice: Vaccine Attitudes Among Religious University Students

by Isaiah Aduse-Poku, Keersty J. B. Thompson, Afton Fillmore, Leah Sim, Isaac A. Woolley, Elizabeth G. Bailey, Brian D. Poole and Jamie L. Jensen

Vaccines 2026, 14(6), 546; https://doi.org/10.3390/vaccines14060546 - 20 Jun 2026

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Abstract

Background/Objectives: Vaccine attitudes are an individual’s beliefs, feelings, and evaluations regarding vaccines. Limited research has examined how students in faith-based university settings organize these attitudes. This study looked at vaccination attitudes among students at a religious university where faith, science, family, and politics [...] Read more.

Background/Objectives: Vaccine attitudes are an individual’s beliefs, feelings, and evaluations regarding vaccines. Limited research has examined how students in faith-based university settings organize these attitudes. This study looked at vaccination attitudes among students at a religious university where faith, science, family, and politics often influence how students think and make decisions. Methods: This study used Q-methodology to examine shared viewpoints about vaccination. A concourse of 240 statements was developed from published literature, public discourse, and student interviews, then reduced to a 37-statement-Q-set. Undergraduate students enrolled in an introductory nonmajors biology course completed digital Q-sorts. We analyzed the data using by-person factor analysis, along with principal components analysis and Varimax rotation. Follow-up interviews helped us interpret the factors. Results: Three viewpoints explained 59% of the study variance. The first viewpoint, Faith-Integrated Institutional Trust, showed strong trust in science, public health agencies, and religious leaders. People in this group saw vaccination as both a moral duty and a way to protect others. The second viewpoint, Skeptical Autonomy and Institutional Distrust, emphasized personal choice, family influence, and distrust of government and official vaccine information. The third viewpoint, Pragmatic Autonomy and Science Confidence, endorsed vaccines and scientific evidence while also prioritizing individual decision-making over mandates. Conclusions: Science alone does not explain vaccination attitudes among college students. Trust, identity, and personal autonomy also play an important role. Vaccine communication should therefore connect scientific evidence with students’ moral commitments, trusted relationships, and concerns about freedom, especially in settings where faith influences health decision-making. Full article

(This article belongs to the Special Issue Acceptance and Hesitancy in Vaccine Uptake: 3rd Edition)

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Graphical abstract

19 pages, 2666 KB

Open AccessArticle

Immunogenicity of a Recombinant Multi-Epitope Vaccine Incorporating GRA14, SAG1, and GRA1 Antigens of Toxoplasma gondii in BALB/c Mice

by Abdulrahman M. Sheikh, Wong Weng Kin, Robaiza Zakaria, Ahmad A. Alshehri, Mohammed Dauda Goni, Abdulrazzag Abdulaziz Othman, Zakeya Al Rasbi, Zeehaida Mohamed and Khalid Hajissa

Vaccines 2026, 14(6), 545; https://doi.org/10.3390/vaccines14060545 - 20 Jun 2026

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Abstract

Background: The high incidence and severe health threat of Toxoplasma gondii (T. gondii) infection, particularly in immunocompromised patients, underscore the urgent need for the development of a safe and effective vaccine. The aim of this study was to develop a novel [...] Read more.

Background: The high incidence and severe health threat of Toxoplasma gondii (T. gondii) infection, particularly in immunocompromised patients, underscore the urgent need for the development of a safe and effective vaccine. The aim of this study was to develop a novel multi-epitope vaccine (USM.TOXOII) incorporating the T. gondii GRA14, SAG1, and GRA1 antigens, and to assess its immunogenicity in BALB/c mice. Methods: Using bioinformatics approach, the USM.TOXOII was designed and evaluated. The encoding gene (471 bp) was then constructed and cloned into the pET-30a (+) plasmid before being transformed into E. coli expression system. The recombinant USM.TOXOII protein was subsequently expressed and purified. Finally, an animal study was performed to assess the vaccine’s immunogenicity. Results: The USM.TOXOII protein (17.27 kDa) was soluble and contained a His tag protein. Immunization of BALB/c mice with USM.TOXOII significantly elevated serum levels of total IgG, IgG1, and IgG2a (p < 0.05). Cytokine analysis revealed a significant increase in IFN-γ production, whereas IL-4 levels remained unchanged, suggesting a Th1-biased immune response. Conclusions: Collectively, these findings indicate that USM.TOXOII possesses immunogenic potential and is capable of inducing both humoral and cellular immune responses in BALB/c mice. Future challenge studies with live T. gondii tachyzoites are warranted to evaluate its protective efficacy in vivo. Full article

(This article belongs to the Special Issue Host–Parasite Interactions and Vaccines)

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13 pages, 962 KB

Open AccessArticle

Incremental Effectiveness of a Second Varicella Vaccine in Children: A Prospective Cohort Study in Anhui, China

by Kun Xuan, Tao Li, Zhenqiu Zha, Shujie Zhou, Feiyang Song, Yu Chai, Xianwei Luo, Xingya Pang, Qingru Li, Fanhong Meng, Zuozhi Xiang, Chaoyin Zhu, Tao Wang, Haiyan Wu, Xiaofeng Huang, Yang Li and Jihai Tang

Vaccines 2026, 14(6), 544; https://doi.org/10.3390/vaccines14060544 - 20 Jun 2026

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Abstract

Background: Varicella remains a common vaccine-preventable disease in China. Although Anhui Province recommended a two-dose varicella vaccine (VarV) schedule in 2021, real-world evidence on the incremental benefit of the second dose is limited. Methods: A prospective cohort study among children aged 1–12 years [...] Read more.

Background: Varicella remains a common vaccine-preventable disease in China. Although Anhui Province recommended a two-dose varicella vaccine (VarV) schedule in 2021, real-world evidence on the incremental benefit of the second dose is limited. Methods: A prospective cohort study among children aged 1–12 years was conducted in Anhui Province from July 2022 to August 2025. Children aged 1–3 years who had received one dose of the human diploid cell line-based (SV-1) VarV and children aged 4–12 years whose second dose was the SV-1 VarV were enrolled in the exposed group and were compared with children who had no history of VarV and those who had received only one dose of the VarV, respectively. Varicella cases were collected through active follow-up and surveillance systems. Vaccine effectiveness (VE) and incremental VE were estimated as [1 − relative risk (RR)] × 100%, where the RRs were calculated based on the incidence densities of breakthrough varicella. Results: Overall, 50,054 participants were finally enrolled, contributing 125,351.5 person-years and 105 valid cases. The VE in children aged 1–3 years was 79.1% (95%CI: 42.8–92.4%). Among children aged 4–12 years, the incremental VE was 65.0% (95%CI: 41.9–78.9%), with incremental VEs of 60.1% (95%CI: 22.3–79.5%) for ages 4–6 years and 72.7% (95%CI: 37.8–88.0%) for ages 7–12 years. Conclusions: One-dose SV-1 VarV provided substantial protection in young children, and a second dose conferred significant additional protection in children aged 4–12 years, supporting strengthened implementation of the two-dose strategy and catch-up vaccination among school-aged children. Full article

(This article belongs to the Special Issue Immunization, Data Analytics, and Surveillance for Vaccine-Preventable Diseases (VPDs))

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21 pages, 6366 KB

Open AccessArticle

Magnetoencephalography Reveals Neuroprotection of COVID-19 Vaccination in Nonhuman Primates

by Jennifer Stapleton-Kotloski, Jared Rowland, April Davenport, Phillip Epperly, Maria Blevins, Dwayne Godwin, Daniel Ewing, Zhaodong Liang, Appavu Sundaram, Nikolai Petrovsky, Kevin Porter, John Sanders and James Daunais

Vaccines 2026, 14(6), 543; https://doi.org/10.3390/vaccines14060543 - 20 Jun 2026

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Abstract

Background/Objectives: COVID-19, caused by the SARS-CoV-2 virus, can lead to widespread neurological and cognitive complications, even in the absence of significant structural brain abnormalities. Understanding the evolving health concerns in the context of viral infections is critical to service member readiness, fitness, and [...] Read more.

Background/Objectives: COVID-19, caused by the SARS-CoV-2 virus, can lead to widespread neurological and cognitive complications, even in the absence of significant structural brain abnormalities. Understanding the evolving health concerns in the context of viral infections is critical to service member readiness, fitness, and mission completion. The potential neuroprotective effects of SARS-CoV-2 vaccination remain underexplored. Methods: Using a cross-sectional, non-human primate model (female cynomolgus macaques), we employed magnetoencephalography (MEG) to assess resting-state brain activity following vaccination with escalating doses of a novel psoralen-inactivated SARS-CoV-2 vaccine (PsIV) or a combination of PsIV and a DNA vaccine (prime boost), and subsequent challenge with the Delta variant (SARS-CoV-2 B.1.617.2). MEG scans were acquired 41 days after inoculation. Source series were constructed for 42 regions of interest for each subject, and band power was computed. Results: Band power demonstrated substantial preservation of neural activity across multiple brain regions in vaccinated subjects compared to unvaccinated controls following viral challenge. Significantly lower power was observed across the brain at all bandwidths in the unvaccinated group relative to the prime boost group. As PsIV concentration increased, spectral power increased, with the prime boost group having the greatest power. Conclusions: This approach not only underscores the role of vaccination in mitigating neuropathology but also highlights the capability of MEG to detect subtle yet significant changes in brain function that may be overlooked by other imaging modalities. These findings advance our understanding of vaccine-induced neuroprotection and establish MEG as a powerful tool for monitoring brain function in the context of viral infections. Full article

(This article belongs to the Special Issue Neurobiological Impacts of Infection, Protective Effects, and Clinical Implications of Vaccines)

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14 pages, 1651 KB

Open AccessSystematic Review

Carriage of Haemophilus influenzae in the Pre- and Post-Hib Vaccine Eras Revisited: A Systematic Review and Meta-Analysis

by Samy Taha, Nouria Belkacem, Ala-Eddine Deghmane and Muhamed-Kheir Taha

Vaccines 2026, 14(6), 542; https://doi.org/10.3390/vaccines14060542 - 20 Jun 2026

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Abstract

Background/Objectives: Re-emergence of Haemophilus influenzae serotype b (Hib) was reported in several European countries. We aimed to characterize the age distribution of H. influnezae carriage before and after Hib vaccination. Methods: We conducted a systematic review and meta-analysis to reassess H. [...] Read more.

Background/Objectives: Re-emergence of Haemophilus influenzae serotype b (Hib) was reported in several European countries. We aimed to characterize the age distribution of H. influnezae carriage before and after Hib vaccination. Methods: We conducted a systematic review and meta-analysis to reassess H. influenzae carriage dynamics in the pre- and post-Hib vaccination eras, focusing on age-specific patterns in childhood. Searches were performed with no date restriction and included PubMed/MEDLINE, Scopus, Web of Science, WHO Global Index Medicus, and the Cochrane Library. Eligible studies reported nasopharyngeal and/or oropharyngeal carriage prevalence and serotype distribution. Pooled estimates with 95% confidence intervals (CIs) were calculated using random-effects models, with age-stratified analyses. Results: Twenty-two studies were included (12 pre- and 10 post-Hib vaccination). Pre-vaccination, pooled H. influenzae carriage prevalence was 24.3% (95% CI, 18.9–30.7%), including 6% (95% CI, 3.4–12.8%) for Hib and 17.5% (95% CI, 12.6–23.9%) for non–type b strains. Post-vaccination, overall carriage remained similar (21.8%; 95% CI, 14.6–31.2%), but Hib carriage declined markedly to 0.67% (95% CI, 0.26–1.71%), while non–type b strains predominated (16.7%; 95% CI, 10.4–25.6%). Meta-analysis showed that carriage peaked around 4–5 years of age and persisted into later childhood. Conclusions: Hib vaccination has reduced Hib carriage, but overall H. influenzae carriage persists due to non–type b strains. Age-related persistence of carriage may have implications for herd protection, particularly in the context of evolving vaccination schedules with early childhood boosters. Continued surveillance integrating carriage and immunological data is needed to inform optimization of vaccination strategies. Full article

(This article belongs to the Section Epidemiology and Vaccination)

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10 pages, 455 KB

Open AccessBrief Report

Fasciculations Following COVID-19 Vaccination—A Case Series of Ten Patients

by Ameli Breuer, Vanessa Raeder, Helena Franziska Pernice, Fabian Boesl, Harald Prüss, Heinrich Audebert, Katrin Hahn and Christiana Franke

Vaccines 2026, 14(6), 541; https://doi.org/10.3390/vaccines14060541 - 19 Jun 2026

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Abstract

Introduction: Vaccination against COVID-19 has been crucial in controlling the pandemic. While side effects are typically mild, rare neurological complications have been reported. This is a case series of ten patients who reported of persistent fasciculations after COVID-19 vaccination. Methods: We describe the [...] Read more.

Introduction: Vaccination against COVID-19 has been crucial in controlling the pandemic. While side effects are typically mild, rare neurological complications have been reported. This is a case series of ten patients who reported of persistent fasciculations after COVID-19 vaccination. Methods: We describe the clinical presentation and diagnostic work-up of ten patients with new-onset fasciculations in temporal proximity to COVID-19 vaccination. Patients with prior SARS-CoV-2 infection or known alternative causes of fasciculations were excluded. Routine clinical data, including neurological examination, laboratory results, and electrophysiology (electromyography and nerve conduction studies), were analyzed. Results: Ten patients (5 male, 5 female; mean age 42.4 years) reported fasciculations beginning within 6 h to 13 days post-vaccination and persisting for 2–12 months at the time of presentation. Fasciculations were accompanied by additional symptoms such as paresthesia and fatigue. Laboratory results were mostly unremarkable; two patients had positive myositis antibodies without clinical correlates. Electrophysiology was unremarkable in six patients, while fasciculation potentials were detected in four patients. Nine were diagnosed with probable benign fasciculation syndrome (BFS), and one met diagnostic criteria for amyotrophic lateral sclerosis (ALS). Discussion: In this small, retrospective case series, most cases of post-vaccination fasciculations were benign and compatible with BFS. Whether BFS onset was causally linked to vaccination or due to a nocebo effect remains unclear. One patient was diagnosed with ALS, though a causal link remains speculative given the study’s limitations and rarity of similar reports. Larger, prospective studies are needed to validate these observations and explore underlying pathophysiological mechanisms. Full article

(This article belongs to the Section COVID-19 Vaccines and Vaccination)

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15 pages, 689 KB

Open AccessArticle

A Phase III, Randomized, Double-Blind, Active-Controlled Non-Inferiority Trial Evaluating the Immunogenicity and Safety of Gardisun, a Quadrivalent Human Papillomavirus Vaccine, Compared with Gardasil^® in Healthy Volunteers Aged 15–35 Years

by Erfan Pakatchian, Minoo Mohraz, Mohammad Taghavian, Babak Javadimehr, Hajar Mohammadi Barzelighi, Majid Teymoori-Rad, Mehrdad Ghodsi and Zahra Naderi Saffar

Vaccines 2026, 14(6), 540; https://doi.org/10.3390/vaccines14060540 - 18 Jun 2026

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Abstract

Background/Objectives: Human papillomavirus (HPV) infection is the leading cause of cervical cancer and is associated with several anogenital and oropharyngeal malignancies. Although licensed HPV vaccines are highly effective, access remains limited in many low- and middle-income countries due to cost, supply shortages, and [...] Read more.

Background/Objectives: Human papillomavirus (HPV) infection is the leading cause of cervical cancer and is associated with several anogenital and oropharyngeal malignancies. Although licensed HPV vaccines are highly effective, access remains limited in many low- and middle-income countries due to cost, supply shortages, and implementation barriers. In this study, we evaluated the immunogenicity and safety of Gardisun, a newly developed quadrivalent prophylactic HPV vaccine, compared with Gardasil^®. Methods: This Phase III randomized, double-blind, active-controlled, parallel-group non-inferiority trial enrolled 450 healthy participants stratified by sex and randomized (1:1) to receive three 0.5 mL intramuscular doses of Gardisun or Gardasil^® on Days 0, 60, and 180. Participants were followed through to Day 210. The primary endpoint was the geometric mean titer (GMT) of antibodies against HPV types 6, 11, 16, and 18 one month after the administration of the third dose. Non-inferiority was defined as the lower bound of the 95% confidence interval (CI) for the GMT ratio exceeding 0.67. Safety was assessed through adverse event monitoring. Results: Of the 450 randomized participants, 422 completed the Month 7 visit and 429 received all three doses. Both vaccines induced antibody responses and seroconversion rates for all HPV types. The primary analysis met the non-inferiority criterion for HPV-6, while prespecified sensitivity analyses supported the existence of non-inferiority across all evaluated HPV types. Most adverse events were mild and transient, with no vaccine-related serious adverse events reported. Conclusions: Gardisun demonstrated robust immunogenicity and a safety profile comparable to that of Gardasil^®, supporting its potential as an accessible alternative quadrivalent HPV vaccine for broader vaccination programs in resource-limited settings. Full article

(This article belongs to the Special Issue Recent Advances and Strategies for the Management of CIN and HPV Eradication Strategies for the Prevention of Uterine Cervical Cancer)

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28 pages, 3537 KB

Open AccessArticle

Protective Effect Against Acute Experimental Toxoplasmosis Conferred by Intranasal Immunisation with Toxoplasma gondii Membrane Proteins Plus CpG Adjuvant

by Carina Brito, Daniela Teixeira, Paula Goulart, Beatriz Rodrigues, Nuno Carvalho, Manuel Vilanova, Alexandra Correia and Margarida Borges

Vaccines 2026, 14(6), 539; https://doi.org/10.3390/vaccines14060539 - 17 Jun 2026

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Abstract

Background: Toxoplasmosis is a prevalent zoonotic disease worldwide, affecting approximately one-third of the global human population. Primary infection with Toxoplasma gondii during pregnancy can induce miscarriage or congenital infection, leading to irreversible damage to the foetus. Moreover, reactivation of T. gondii infection in [...] Read more.

Background: Toxoplasmosis is a prevalent zoonotic disease worldwide, affecting approximately one-third of the global human population. Primary infection with Toxoplasma gondii during pregnancy can induce miscarriage or congenital infection, leading to irreversible damage to the foetus. Moreover, reactivation of T. gondii infection in immunosuppressed individuals can result in fatal outcomes. No vaccine exists to prevent human disease caused by this parasite. Thus, a vaccine that could induce complete and lasting protection against human toxoplasmosis is an unmet need. Method: In this work, BALB/cByJ mice were intranasally immunised with a subunit vaccine consisting of T. gondii membrane proteins (TGMP) from the T. gondii Me49 strain plus CpG-oligodeoxynucleotide adjuvant (CpG). Antibody responses were analysed by ELISA, while T-cell responses were evaluated by flow cytometry. The immunogenic proteins present in TGMP were identified by mass spectrometry, and parasite burden was quantified by qPCR. Result: The results showed raised TGMP-specific serum IgG and intestinal IgA antibody levels, and parasite-specific IFN-γ-producing CD4⁺ and CD8⁺ memory T cells. Dense granule proteins (GRA) 2 and 7, surface antigen (SAG)-related sequences 25, 29B, and 34A, microneme protein (MIC) 10, toxofilin, nascent polypeptide-associated complex (NAC) domain-containing protein, and NAC subunit beta were identified as immunogenic proteins. Mice immunised with TGMP+CpG were challenged with T. gondii tachyzoites and showed a significant reduction in the parasitic burden in the peritoneal exudate, spleen, and lungs, compared to mice sham-immunised with CpG alone. Conclusions: Altogether, these results indicate that mucosal immunisation with TGMP plus CpG adjuvant is worth exploring as a vaccination approach to prevent toxoplasmosis. Full article

(This article belongs to the Special Issue Anti-Parasitic Vaccines and Host Immune Responses)

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15 pages, 749 KB

Open AccessArticle

Childhood Vaccine Refusal: Sociodemographic, Behavioral, and Vaccine Confidence Factors in Konya, Türkiye

by Önder Aydemir, Elif Nur Yıldırım-Öztürk and Mehmet Koç

Vaccines 2026, 14(6), 538; https://doi.org/10.3390/vaccines14060538 - 17 Jun 2026

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Abstract

Background/Objectives: Childhood vaccine refusal may negatively affect immunization programs in Türkiye, where regional clusters of hesitancy have emerged despite high national coverage. This study aimed to identify sociodemographic, behavioral, and vaccine confidence-related factors independently associated with childhood vaccine refusal in Konya, Türkiye. Methods: [...] Read more.

Background/Objectives: Childhood vaccine refusal may negatively affect immunization programs in Türkiye, where regional clusters of hesitancy have emerged despite high national coverage. This study aimed to identify sociodemographic, behavioral, and vaccine confidence-related factors independently associated with childhood vaccine refusal in Konya, Türkiye. Methods: An unmatched case–control study was conducted between July and October 2025 in family health centers across Konya. Cases were parents who had refused at least one routine childhood vaccine (n = 406); controls were parents whose children had completed all routine vaccinations (n = 412). Data were collected through face-to-face interviews using a 47-item structured questionnaire and the Turkish version of the Vaccine Hesitancy Scale (VHS). Independent associations were assessed using multivariable logistic regression, with multicollinearity evaluated by variance inflation factors. Results: Maternal employment (aOR = 0.371, 95% CI: 0.218–0.633), parental COVID-19 vaccination (aOR = 0.131, 95% CI: 0.086–0.200), mother’s complete childhood immunization (aOR = 0.418, 95% CI: 0.262–0.667), tetanus vaccination during pregnancy (aOR = 0.259, 95% CI: 0.159–0.421), and neonatal vitamin K administration (aOR = 0.256, 95% CI: 0.132–0.497) were independently associated with lower refusal odds. Higher number of children (aOR = 1.281) and perceived vaccine-related adverse events in the social environment (aOR = 16.982, 95% CI: 9.914–29.089) increased refusal odds. VHS scores were significantly lower in the refusal group (22.2 ± 6.4 vs. 39.8 ± 6.5; p < 0.001), indicating greater hesitancy. Notably, 21.9% of refusing parents reported being advised by a healthcare professional not to vaccinate. Conclusions: Childhood vaccine refusal in Konya was associated with sociodemographic, behavioral, preventive health-related, and vaccine confidence-related factors. The findings suggest relatively reduced engagement with selected preventive health practices, greater reliance on non-professional information sources, and lower vaccine confidence among refusing parents. Interventions should focus on strengthening healthcare-professional communication, trust-building, transparent risk communication, and evidence-based social media strategies. Full article

(This article belongs to the Special Issue Acceptance and Hesitancy in Vaccine Uptake: 3rd Edition)

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16 pages, 1114 KB

Open AccessArticle

Pakistan’s 2025 HPV Vaccine Phase I Rollout: Community Response, Implementation Challenges & Way Forward

by Wei Xia, Soofia Yunus, Atta Ur Rehman, Shah Nawaz Jiskani, Muhammad Imran Qureshi, Shawana Farooq, Inam Bhatti, Sunday Audu, Syed Natiq Abbas Kazmi and Rozina Khalid

Vaccines 2026, 14(6), 537; https://doi.org/10.3390/vaccines14060537 - 17 Jun 2026

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Abstract

Background: The International Agency for Research on Cancer estimated around 3197 annual deaths along with 5008 newly diagnosed cases of cervical cancer in Pakistan. Worldwide, introduced in 164 WHO member states, the HPV vaccine provides over ninety percent (90%) protection from human papillomavirus [...] Read more.

Background: The International Agency for Research on Cancer estimated around 3197 annual deaths along with 5008 newly diagnosed cases of cervical cancer in Pakistan. Worldwide, introduced in 164 WHO member states, the HPV vaccine provides over ninety percent (90%) protection from human papillomavirus (16 & 18 types) infections. This article intended to document the vaccine (HPV) introduction in a low-middle-income country through the lens of EPI preparedness, vaccination coverage achieved, community acceptance, and implementation challenges during Phase I. Methodology: The research applied a qualitative and quantitative mix method to review the intricate procedure of new vaccine rollout within the national context. A qualitative participant observation approach assessed the planning, approval, and implementation phases of the HPV vaccine. Quantitative data statistics were evaluated for national & regional vaccination coverages, rapid convenience assessment findings, and adverse events reports. Results: The overall reported administrative HPV campaign coverage was 75%, with the maximum regional coverage of 81% by the Punjab, followed by 66% of the Sindh, 43% by the Azad Jammu & Kashmir, and 38% by the Islamabad. Rapid Convenience Assessment findings highlighted the main reasons for refusal (71%), with unavailable girls during the campaign (22%) for non-HPV vaccination. Community acceptance varied across the regions, with notable challenges in implementation being observed. Discussion & Way Forward: Initial phase campaign coverage (70.6%) was greater than the worldwide reported first dose mean coverage (61.6%) for the same multi-age cohort, indicative of an encouraging start in resource limited setting. Documented coverage was below the high-performing countries but comparable to multiple low and middle-income countries. Federal Directorate of Immunization, in collaboration with provincial EPI stakeholders, should prioritize including the newly introduced HPV vaccine in the routine immunization schedule of the Phase I regions and should also implement the lessons learned in the subsequent rollout phases in 2026 in Khyber Pakhtunkhwa and 2027 in Balochistan & Gilgit Baltistan. Expanding fixed EPI sites for HPV vaccination, promoting school-centered vaccination, rationalizing outreach in marginalized areas, sustaining the cold chain system, implementing a culturally acceptable communication plan, and resolving internet connectivity challenges are the key strategies to address implementation challenges. Full article

(This article belongs to the Special Issue HPV Vaccination and Primary HPV Screening)

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19 pages, 310 KB

Open AccessReview

Maternal Vaccine Acceptance and Attitudes Before and After the COVID-19 Pandemic: A Narrative Literature Review

by Barbara Frączek, Karolina Pieniawska-Śmiech, Mateusz Babicki, Bartosz Balcer, Natalia Dolata, Dagmara Pokorna-Kałwak and Karolina Kłoda

Vaccines 2026, 14(6), 536; https://doi.org/10.3390/vaccines14060536 - 17 Jun 2026

Viewed by 398

Abstract

Objectives: This study aims to assess the acceptance of vaccinations among pregnant women, particularly against influenza, pertussis, COVID-19, and RSV, and to identify factors influencing their willingness to get vaccinated. It also seeks to evaluate the impact of the COVID-19 pandemic on maternal [...] Read more.

Objectives: This study aims to assess the acceptance of vaccinations among pregnant women, particularly against influenza, pertussis, COVID-19, and RSV, and to identify factors influencing their willingness to get vaccinated. It also seeks to evaluate the impact of the COVID-19 pandemic on maternal attitudes and behaviors regarding vaccination. Methods: The analysis involved a review of existing literature and studies to evaluate the level of vaccine acceptance among pregnant women before and after the COVID-19 pandemic. Factors contributing to vaccine hesitancy, including misinformation, lack of knowledge, and the influence of healthcare professionals, were examined. Results: The findings indicated that, despite scientific evidence supporting the safety and efficacy of vaccines during pregnancy, public concerns remain about their impact on the developing fetus. The outbreak of the COVID-19 pandemic has increased awareness of the risk of infectious diseases, but at the same time, its impact on vaccination rates among pregnant women is ambiguous and geographically diverse. Misinformation and decreased access to healthcare during the pandemic negatively affected vaccine uptake. Trustworthy information provided by healthcare professionals emerged as a key factor in promoting vaccine acceptance. Conclusions: To improve vaccination rates among pregnant women, it is essential to provide clear, evidence-based information through healthcare professionals, particularly those directly caring for pregnant women. Educational campaigns should address concerns calmly and without judgment, emphasizing the safety and benefits of vaccinations. Enhanced access to healthcare and vaccinations, along with strategic information dissemination, can significantly improve vaccine acceptance during pregnancy. Lessons learned from past pandemics should be incorporated into the development of healthcare strategies aimed at implementing recommended vaccinations for pregnant women in the future. Full article

(This article belongs to the Special Issue Maternal Vaccination and Vaccines—2nd Edition)

16 pages, 10132 KB

Open AccessOpinion

Proposed Conceptual and Experience-Based Framework for Reaching an Optimal Vaccine Launch Strategy

by Baudouin Standaert and Marc Raes

Vaccines 2026, 14(6), 535; https://doi.org/10.3390/vaccines14060535 - 16 Jun 2026

Viewed by 343

Abstract

Obtaining market approval and reimbursement are necessary but not sufficient conditions for the implementation of new vaccines in high-income countries to maximize their long-term preventative value. Comprehensive pre-launch and launch-phase economic evaluations of the disease and the vaccine are necessary to support long-term [...] Read more.

Obtaining market approval and reimbursement are necessary but not sufficient conditions for the implementation of new vaccines in high-income countries to maximize their long-term preventative value. Comprehensive pre-launch and launch-phase economic evaluations of the disease and the vaccine are necessary to support long-term public health improvement by the vaccination program. This review highlights the construction of these evaluations conceived as a plan, methods, and a tool. They can be generated by different stakeholders (e.g., payers, producers, target groups) interested in the value success of vaccination. A Vaccine Launching Value Project (VLVP) has been developed based on the experience gained from helping to launch 10 new vaccines worldwide over 15 years (2005–2020). It comprises information on the following: (1) identification of new vaccines that should require a VLVP approach; (2) country-specific characteristics of healthcare; (3) methods to assess economic values for specific stakeholders; (4) identification of the money flow in managing the disease and infection spread; and (5) optimal implementation strategies at the initiation of new vaccination programs. The benefits of applying the VLVP are illustrated using rotavirus vaccination as an example. The VLVP program starts with the development of a Broad Country Linked Inventory (Brocoli) Plan that interconnects eight baskets of information specifying a framework of activities. This is followed by the Cauliflower and Artichoke Methods to assess the vaccine value for additional key stakeholders (e.g., employers, hospital managers, working mothers, the Ministry of Finance) and the money flow amongst the payers (who pays what to whom, when, for what, and how). The evaluation process finishes with the Total Management Tool (Tomato) to identify the optimal implementation conditions at the start of a new vaccination program necessary to obtain the best long-term value for the stakeholders selected. The critical interconnections between these information blocks are discussed. This improves the positioning of a new vaccine by articulating its total economic value within a societal and public health environment over time, outside the conventional Health Technology Assessment box. The Tomato Tool emerges as the most pivotal component of the VLVP. It provides the best assurance of long-term economic value with strong sustainability support. Full article

(This article belongs to the Special Issue Vaccination and Global Health Equity: Innovations, Access, and Impact)

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17 pages, 2214 KB

Open AccessArticle

Development and Qualification of a Nipah Virus Glycoprotein-Specific IgG ELISA for the Assessment of Human Antibody Responses

by Mohammad Mamun Alam, Tahsin Tabassum Anonto, Sinthia Karim, Gathoni Kamuyu, Ali Azizi, Ayesha Siddika, Shadman Sakib Choudhury, Md Wasik Rahman, Anika Farzin, Dewan Imtiaz Rahman, Rubhana Raqib, Mustafizur Rahman, Sharmin Sultana, Trevor Shoemaker, Michael K. Lo, Sayera Banu, Tahmina Shirin, Christina F. Spiropoulou, Joel M. Montgomery, Syed Moinuddin Satter and Mohammed Ziaur Rahman Show full author list Hide full author list

Vaccines 2026, 14(6), 534; https://doi.org/10.3390/vaccines14060534 - 16 Jun 2026

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Abstract

Background/Objectives: Nipah virus (NiV) is a highly pathogenic zoonotic virus with fatality rates exceeding 70% and causes recurring outbreaks in South and Southeast Asia. Reliable serological assays are critical for outbreak surveillance, diagnosis, and evaluation of vaccine-induced immune responses. This study aimed to [...] Read more.

Background/Objectives: Nipah virus (NiV) is a highly pathogenic zoonotic virus with fatality rates exceeding 70% and causes recurring outbreaks in South and Southeast Asia. Reliable serological assays are critical for outbreak surveillance, diagnosis, and evaluation of vaccine-induced immune responses. This study aimed to develop and qualify an indirect enzyme-linked immunosorbent assay (ELISA) based on recombinant NiV glycoprotein G for the detection of virus-specific IgG antibodies in human serum. Methods: An indirect ELISA was developed and optimized for antigen concentration, blocking conditions, and serum dilution. The assay performance was evaluated using convalescent human sera from Bangladesh, along with the World Health Organization (WHO) International Standard for anti-Nipah virus antibodies, maintained and distributed by the National Institute for Biological Standards and Control (NIBSC). Analytical validation was conducted in accordance with ICH Q2 (R2) guidelines, including assessments of sensitivity, specificity, Precision, Linearity, and detection limits. Results: The assay demonstrated 100% sensitivity and specificity relative to reference sera. Intra-assay coefficients of variation ranged from 0.36% to 5.73%, and inter-assay variation was 4.16%, indicating high precision. The ELISA showed excellent Linearity (R² > 0.995). The lower limit of detection was 0.51 IU/mL, and the lower limit of quantification was 0.98 IU/mL. Conclusions: The developed ELISA is a BSL-2-compatible, robust, and scalable platform suitable for serosurveillance and the assessment of vaccine-induced immunity in endemic regions. Calibration against an international standard supports its applicability for standardized antibody measurement. This assay provides a practical tool for NiV outbreak response and vaccine evaluation. Full article

(This article belongs to the Section Vaccines, Clinical Advancement, and Associated Immunology)

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19 pages, 4626 KB

Open AccessArticle

Antibody Titres to Strangvac^® Antigens Correlate with Protection and Duration of Immunity Against Experimental Infection with Streptococcus equi Subspecies equi

by Romain Paillot, Francesco Righetti, Carl Robinson, Lars Frykberg, Margareta Flock, Olof Zachrisson, Bengt Guss, Jan-Ingmar Flock and Andrew S. Waller

Vaccines 2026, 14(6), 533; https://doi.org/10.3390/vaccines14060533 - 16 Jun 2026

Cited by 1 | Viewed by 579

Abstract

Background/Objectives: Strangles, caused by Streptococcus equi subspecies equi (S. equi), remains a common and severe equine infectious disease. Strangvac^®, a recombinant fusion protein vaccine licenced in Europe, contains the antigens (Ag) CCE, Eq85, IdeE and a saponin adjuvant. Although [...] Read more.

Background/Objectives: Strangles, caused by Streptococcus equi subspecies equi (S. equi), remains a common and severe equine infectious disease. Strangvac^®, a recombinant fusion protein vaccine licenced in Europe, contains the antigens (Ag) CCE, Eq85, IdeE and a saponin adjuvant. Although its efficacy is high (94% in clinical trials and 100% in some natural outbreaks), immune correlates of protection have not been defined. This study determined the antibody (Ab) thresholds predictive of protection against clinical disease following high-dose experimental S. equi infection and the expected levels of protection at 6 and 12 months after V2. Methods: This study was a retrospective analysis of six independent double-blinded placebo-controlled experimental infection studies involving 129 ponies (80 vaccinated controls and 49 placebo controls) and a serology study (12 vaccinated ponies). Ponies received two to five vaccine doses before being experimentally challenged with S. equi strain Se4047. Ponies in the serology study were not experimentally infected. The onset of pyrexia (≥39 °C for at least 2 of 3 consecutive days, OOT) was used as a disease marker. Serology to IdeE, Eq85 and CCE was analysed with standardised clinical outcomes to define protective thresholds through correlation and Receiver Operating Characteristic (ROC) analyses. The predicted level of protection up to one year after V2 was then calculated (duration of immunity: DOI). Results: A protection threshold of ≥10 days to OOT, derived from the control distribution, was used for ROC modelling. Predictive performance (e.g., accuracy, precision, specificity) was calculated for individual and combined Ab thresholds. All controls developed pyrexia (median 6 days, IQR 5–7), with 46 out of 49 (93.9%) within 9 days of the challenge. Vaccinated ponies showed significantly delayed or absent OOT compared with controls (p < 0.0001), with 37 vaccinated ponies (46.25%) reaching the end of the studies without developing pyrexia. The Ab titre to all antigens was significantly associated with the level of protection (p < 0.0001). ROC analyses demonstrated high discriminative power (AUC 0.86–0.88). Optimal Ab titre boundaries yielded high precision (≥80%) for all Ags (IdeE: 3.5–4.3; Eq85: 2.65–3.7 and CCE: 2.66–3.2). Both precision and accuracy remained above 80% for levels of IdeE and Eq85 Ab titres superior or equal to those measured up to one year after V2, with an estimated level of protection of 78.9% to 81.2% in vaccinated animals. Conclusions: Ab titres to all three Ags represent robust correlates of protection against pyrexia following high-dose experimental S. equi challenge in Strangvac^®-vaccinated ponies. Ab titres measured up to one year after V2 were estimated to continue to provide significant protection in vaccinated animals. These findings support the observed levels of protection conferred by Strangvac^® against natural infection with S. equi. Full article

(This article belongs to the Section Veterinary Vaccines)

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21 pages, 4408 KB

Open AccessArticle

Deciphering the Nodamura virus Protein A Function in Schizosaccharomyces pombe and Engineering a Novel Self-Amplifying RNA (saRNA) Vector NovaVec for Vaccine Development

by Xueyao Song, Ruihan Liu, Zhuo Zhang, Yuying Pan, Wanting Qu, Niubing Zhang, Xuan Li, Xiangping Yao and Pei Hao

Vaccines 2026, 14(6), 532; https://doi.org/10.3390/vaccines14060532 - 15 Jun 2026

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Abstract

Background/Objectives: Self-amplifying RNA (saRNA) vectors enable high-level transgene expression from minimal initial doses. While alphavirus-based saRNA systems are widely used, they suffer from limitations, including large genome size, complex replicase machinery, and cellular toxicity. Nodamura virus (NoV) offers a promising alternative due to [...] Read more.

Background/Objectives: Self-amplifying RNA (saRNA) vectors enable high-level transgene expression from minimal initial doses. While alphavirus-based saRNA systems are widely used, they suffer from limitations, including large genome size, complex replicase machinery, and cellular toxicity. Nodamura virus (NoV) offers a promising alternative due to its compact genome (3.2 kb) and low cytotoxicity. This study aimed to elucidate NoV RNA1 replication mechanisms and develop a novel NoV-based saRNA vector platform. Methods: We established a Schizosaccharomyces pombe system to investigate NoV RNA1 replication and protein A localization. N-terminal deletion mutants and ER-targeting chimeras were constructed to characterize membrane targeting determinants. Based on mechanistic insights, we developed NovaVec by inserting transgenes at the RNA3⁴²² site within the subgenomic RNA3 region. In vivo performance was evaluated using lipid nanoparticle-encapsulated NovaVec expressing nanoluciferase or monkeypox A33R antigen in BALB/c mice. Results: We identified redundant mitochondrial targeting domains (amino acids 2-15 and 16-33) in NoV protein A, where either domain was sufficient for proper localization and replication. The replication machinery could be functionally redirected to the endoplasmic reticulum while maintaining replication competence. Lipid nanoparticle-encapsulated NovaVec achieved sustained transgene expression for 54 days in mice, significantly outperforming conventional mRNA vectors that lost signal within 14 days. The NovaVec-based monkeypox A33R vaccine elicited robust antigen-specific humoral immunity with titers reaching approximately 1:12,800 following booster immunization. Conclusions: With its compact genome encoding only a single replicase protein, minimal cytopathic effects, and demonstrated capacity for long-term protein expression, NovaVec represents a highly promising next-generation saRNA platform for vaccines. Full article

(This article belongs to the Special Issue Bioengineering Strategies for Developing Vaccines)

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12 pages, 1105 KB

Open AccessArticle

Longevity and Magnitude of Antibody Responses After Homologous and Heterologous COVID-19 Booster Vaccinations in Bangladesh

by Marjahan Akhtar, Md. Rashedul Islam, Zahid Hasan Khan, Afroza Akter, Imam Tauheed, Tasnuva Ahmed, Ishtiakul Islam Khan, Mohammad Ashraful Amin, Fatema Khaton, Farhana Khanam, Md. Taufiqul Islam, Prasanta Kumar Biswas, Rumana Rashid, Md. Mamunur Rashid, Md. Zakir Hossain, Ahmed Nawsher Alam, A. S. M. Alamgir, Edward T. Ryan, Sayera Banu, Tahmina Shirin, Fahima Chowdhury, Ashraful Islam Khan, Taufiqur Rahman Bhuiyan and Firdausi Qadri Show full author list Hide full author list

Vaccines 2026, 14(6), 531; https://doi.org/10.3390/vaccines14060531 - 15 Jun 2026

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Abstract

Background: The dynamics of humoral immune responses following primary and booster COVID-19 vaccinations are crucial to understand in order to optimize vaccination strategies. This study evaluates the magnitude and durability of SARS-CoV-2-specific IgG antibody responses across different vaccines in a large cohort of [...] Read more.

Background: The dynamics of humoral immune responses following primary and booster COVID-19 vaccinations are crucial to understand in order to optimize vaccination strategies. This study evaluates the magnitude and durability of SARS-CoV-2-specific IgG antibody responses across different vaccines in a large cohort of Bangladeshi adults. Methods: A total of 6300 adults from nine hospitals across eight divisions of Bangladesh were enrolled. Participants received two primary doses of either ChAdOx1 nCoV-19 (Covishield, Serum Institute of India, n = 2855), mRNA-1273 (Moderna, n = 578), BNT162b2 (Pfizer-BioNTech, n = 121), or Vero-cell-inactivated (Sinopharm, n = 2746) vaccines. Booster doses were administered at one-year intervals post-primary vaccination. SARS-CoV-2 spike receptor-binding domain (RBD)-specific IgG antibody responses were measured by ELISA using serum from vaccinees at multiple time points after two primary and two booster doses. Results: A total of 3745 individuals received booster 1 (third dose), with 59% receiving heterologous boosters (a different vaccine regimen than the primary doses). Only 5.5% (n = 347) of participants received a second booster one year after the first booster (among them, 99% received BNT162b2). Our results suggest that heterologous boosters with the mRNA vaccine induced higher IgG levels than homologous boosters for individuals who received primary vaccination with adenovirus vector-based ChAdOx1 nCoV-19 or a Vero-cell-inactivated vaccine. However, in those who initially received the mRNA-based vaccine, both homologous and heterologous boosters produced comparable IgG responses. Among all vaccine types, booster immunization with the Vero-cell-inactivated vaccine induced the lowest antibody responses. Longitudinal analysis demonstrated significantly high IgG levels over the 12 months following the first booster (p < 0.0001); however, IgG levels declined significantly after the second booster dose (fourth dose). Conclusions: Heterologous boosting strategies, particularly those involving mRNA vaccines, elicit stronger and more sustained IgG responses compared to a homologous booster. However, antibody waning after the second booster highlights the need for continued monitoring and potential additional vaccine strategies. Full article

(This article belongs to the Special Issue COVID-19 Vaccines in the Post-Pandemic Era: Immune Responses, Boosting Strategies, and Long-Term Outcomes)

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14 pages, 248 KB

Open AccessArticle

Knowledge, Attitudes and Perceived Barriers to Pneumococcal Vaccination: A Cross-Sectional Survey Among Healthcare Workers and Administrative Staff at an Italian University Hospital

by Giulia Congedo, Rossella Mancini, Fabio Pattavina, Domenico Pascucci, Stefania Bruno and Patrizia Laurenti

Vaccines 2026, 14(6), 530; https://doi.org/10.3390/vaccines14060530 - 15 Jun 2026

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Abstract

Introduction: Streptococcus pneumoniae severely affects adults over 65, especially those with comorbidities. Since vaccination coverage among healthcare workers (HCWs) is unknown despite free availability, this study evaluates knowledge, behaviours, hesitancy and accessibility among employees of an Italian hospital. Methods: A prospective [...] Read more.

Introduction: Streptococcus pneumoniae severely affects adults over 65, especially those with comorbidities. Since vaccination coverage among healthcare workers (HCWs) is unknown despite free availability, this study evaluates knowledge, behaviours, hesitancy and accessibility among employees of an Italian hospital. Methods: A prospective cross-sectional survey was administered via “SurveyMonkey.” From February 22 to June 15, 2024, healthcare and administrative staff aged ≥ 18 at the Fondazione Policlinico Universitario Gemelli were recruited by email. Descriptive and inferential analyses used Stata 16.1. Results: Among HCWs, 72% are women, with an average age of 48. Pneumococcal vaccination coverage is 20%, with 82.7% vaccinated in-hospital. Preferred information sources include courses, webinars, and institutional websites. For management staff, vaccine safety and effectiveness were significant determinants. Among administrative employees, 65% are women (average age 51); 19% are vaccinated, 24% are unsure, and 43% prefer in-hospital vaccination. Physicians cited trust in vaccines (25.3%) and self-protection (23.2%) as key motivators, compared with 12.4% among nursing, technical and rehabilitative staff. Recommendation to family members was higher among medical and specialist professionals (90%) than in other groups (77% in nursing/technical/rehabilitative; <50% in assistants and auxiliary staff). About half of the groups rated their knowledge at level 2 (scale 1–4). Multivariable regression analysis showed that medical professionals and specialists exhibited a higher perception of the importance and safety of vaccines compared with other categories. Conclusions: HCWs showed greater knowledge of pneumococcal vaccination, while administrative staff had lower awareness and more hesitancy. Both groups preferred in-hospital vaccination and expressed interest in structured educational initiatives. Full article

(This article belongs to the Special Issue Acceptance and Hesitancy in Vaccine Uptake: 3rd Edition)

17 pages, 2901 KB

Open AccessArticle

Knowledge, Awareness, and Willingness Toward the HPV Vaccine Among Medical Students at Qassim University: A Cross-Sectional Study

by Ghadah Alhetheli, Rifal Alhumaid, Shams Alajlan, Sheyam Alajlan, Lamia Alharbi, Lamis Allahim and Hala Ahmed Alrubah

Vaccines 2026, 14(6), 529; https://doi.org/10.3390/vaccines14060529 - 15 Jun 2026

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Abstract

Background: Human papillomavirus (HPV) causes nearly all cervical cancers and a growing share of HPV-related malignancies in both sexes, yet HPV vaccine knowledge and acceptance among medical students in Saudi Arabia, the next generation of clinicians shaping recommendations, remain poorly characterized across the [...] Read more.

Background: Human papillomavirus (HPV) causes nearly all cervical cancers and a growing share of HPV-related malignancies in both sexes, yet HPV vaccine knowledge and acceptance among medical students in Saudi Arabia, the next generation of clinicians shaping recommendations, remain poorly characterized across the full training continuum. Methods: We conducted a cross-sectional online survey of 300 medical students at the College of Medicine, Qassim University. A pre-validated questionnaire captured sociodemographic data, HPV knowledge (14 items), vaccine awareness, attitudes and behavioral intent (4 items), and barriers. Multivariable logistic regression assessed independent predictors of awareness, personal willingness, and intent to recommend the vaccine to family members and future patients. Results: A total of 91.7% of students had previously heard of HPV, and 79.3% had heard of the HPV vaccine. However, only 44.3% reached the predefined threshold for good knowledge, and 56.3% reported personal willingness to receive the vaccine. Willingness to recommend the vaccine to future patients was the most frequently endorsed intent (78.3%), followed by recommending it to a family member (73.3%), with male gender reported as the leading reason among decliners. After adjustment, each one-point increase in the knowledge score independently raised the adjusted odds of vaccine awareness (aOR 1.40, 95% CI 1.22 to 1.61), of recommending the vaccine to a future patient (aOR 1.28, 95% CI 1.13 to 1.45), of recommending it to a family member (aOR 1.19, 95% CI 1.06 to 1.33), and of personal willingness (aOR 1.16, 95% CI 1.04 to 1.29). Female gender was associated with higher odds of personal willingness (aOR 2.31, 95% CI 1.37 to 3.88), and senior training phase predicted vaccine awareness (aOR 2.71, 95% CI 1.33 to 5.52). Conclusions: Human papillomavirus vaccine knowledge independently predicted both awareness and behavioral intent among medical students at Qassim University. However, personal willingness to receive the vaccine lagged behind willingness to recommend it, particularly among male students. Embedding HPV prevention more explicitly into the medical curriculum, with particular emphasis on its relevance to male health, may help narrow this gap. Full article

(This article belongs to the Section Vaccination Against Cancer and Chronic Diseases)

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11 pages, 831 KB

Open AccessReview

From Local Pilots to National Implementation: A Journey Towards Free HPV Vaccination in China

by Yinqi He, Yihan Fu, Zhitao Wang and Jing Sun

Vaccines 2026, 14(6), 528; https://doi.org/10.3390/vaccines14060528 - 15 Jun 2026

Viewed by 359

Abstract

China recently became the 155th country to provide free vaccination to all 13-year-old girls with two doses of a domestic bivalent HPV vaccine in October 2025. Such a policy change aligns with the Immunization Agenda 2030, which expects more investment of domestic resources [...] Read more.

China recently became the 155th country to provide free vaccination to all 13-year-old girls with two doses of a domestic bivalent HPV vaccine in October 2025. Such a policy change aligns with the Immunization Agenda 2030, which expects more investment of domestic resources into immunization rather than heavily depending on external donor funding support. This review examines the policy-making evolution process and analyzes how the final decision was made at the national level, using the Multiple Streams Framework. Unlike traditional NIP expansion, which adopts a top-down decision-making strategy, China’s free HPV vaccination policy evolved with a distinct bottom-up strategy originating from local pilots, which is demonstrated to be instrumental for national policy-making. The extensive local pilots of free HPV vaccination have served as a powerful engine that drives a rapid and substantial increase in HPV vaccination rate, played a pivotal role in shaping the market of HPV vaccines, and contributed to achieving the economies of scale, which triggered a substantial price reduction. It also fostered a national consensus on the critical role of HPV vaccination in cervical cancer prevention and control, a principle now enshrined in the core public health knowledge repository across the country. A potential strategy to introduce new vaccines into the NIP could be piloting first and expanding incrementally with the bottom-up strategy, leveraging a comprehensive platform under the framework of the national policy, and then making use of the effect of scale and peer pressure, high level engagement, cross-departmental collaboration, and multiple financing mechanisms. Full article

(This article belongs to the Special Issue HPV Vaccination and Primary HPV Screening)

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4 pages, 165 KB

Open AccessEditorial

Immunity to Influenza Viruses and Vaccines: From Broader Immunity to Chrono-Optimization and Safety

by Rongbao Gao

Vaccines 2026, 14(6), 527; https://doi.org/10.3390/vaccines14060527 - 14 Jun 2026

Viewed by 285

Abstract

Influenza viruses remain a formidable challenge to global public health, causing annual epidemics and intermittent pandemics, and resulting in over 3 million severe infections with 290,000–650,000 deaths annually [...] Full article

(This article belongs to the Special Issue Immunity to Influenza Viruses and Vaccines)

20 pages, 2632 KB

Open AccessArticle

Long-Lasting Antibody and CD8⁺ Memory T Cell Responses Induced by N-Tc52/TSKb20 Vaccination upon Trypanosoma cruzi Antigen Re-Encounter

by María Elisa Vázquez, Brenda A. Zabala, Maria Constanza Barrientos, Daniela E. Barraza, María A. Occhionero, Federico Ramos, Alejandro Uncos, Leonardo Acuña and Cecilia Pérez Brandán

Vaccines 2026, 14(6), 526; https://doi.org/10.3390/vaccines14060526 - 13 Jun 2026

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Abstract

Background: Chagas disease, caused by Trypanosoma cruzi, remains a major public health problem in Latin America and an emerging concern worldwide. Current chemotherapies show limited efficacy during chronic infection, and no licensed vaccine is currently available. We previously developed the chimeric [...] Read more.

Background: Chagas disease, caused by Trypanosoma cruzi, remains a major public health problem in Latin America and an emerging concern worldwide. Current chemotherapies show limited efficacy during chronic infection, and no licensed vaccine is currently available. We previously developed the chimeric antigen N-Tc52/TSKb20 as a vaccine candidate against T. cruzi infection. In a murine model, this vaccine induced robust antigen-specific immune response associated with protection shortly after vaccination. Objectives: Here, we investigated the long-term persistence and effector functions of the immune responses elicited by this vaccine candidate. Methods: Both female and male C57BL/6 mice were immunized with three doses of N-Tc52/TSKb20 formulated with QuilA adjuvant. Serum samples collected 170 days post-immunization were analyzed for antigen-specific antibodies by ELISA and for trypanolytic activity against cell-derived trypomastigotes using an in vitro functional assay. Cellular immune responses were evaluated by measuring cytokine production, T cell activation, and memory T cell responses following in vitro re-stimulation with the vaccine antigen or T. cruzi antigens. Results: N-Tc52/TSKb20 vaccination induced a sustained antigen-specific humoral response, characterized by long-lasting IgG2c antibodies and functional activity persisting for up to 170 days post-immunization. In parallel, vaccination promoted long-term activation of antigen-specific CD8⁺ T cells and production of TNF-α and IFN-γ upon antigen re-encounter. A sex-dependent tendency was observed for IL-10, with increased production in vaccinated female mice. Moreover, vaccinated animals exhibited increased frequencies of central and effector memory CD4⁺ and CD8⁺ T cells in response to T. cruzi antigens, with a predominant contribution of CD8⁺ T cells, indicating the establishment of parasite-specific T cell memory. Conclusions: Together, these findings demonstrate that vaccination with N-Tc52/TSKb20 induces a long-lasting Th1-biased immune response characterized by trypanolytic antibodies, functional and durable T cell responses, and parasite-specific memory T cells. This immunological profile supports the potential of N-Tc52/TSKb20 as a promising vaccine candidate for Chagas disease and highlights its capacity to elicit immune mechanisms that have been associated with protection against T. cruzi infection. Full article

(This article belongs to the Special Issue Innovative Vaccines and Technologies to Address Tropical Parasitic Diseases)

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42 pages, 5124 KB

Open AccessReview

Chimeric Pathogen-Associated Molecular Patterns (PAMPs) as Vaccine Adjuvants

by Bethany M. Potter, Anya F. Weth, Emma M. Dangerfield, Mattie S. M. Timmer and Bridget L. Stocker

Vaccines 2026, 14(6), 525; https://doi.org/10.3390/vaccines14060525 - 12 Jun 2026

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Abstract

The development of pathogen-associated molecular patterns (PAMPs) that signal via pathogen recognition receptors (PRRs) on innate immune cells is a strategy that is widely adopted in adjuvant research. Less well studied is how covalently linking different PAMPs affects the immune response. Herein, we [...] Read more.

The development of pathogen-associated molecular patterns (PAMPs) that signal via pathogen recognition receptors (PRRs) on innate immune cells is a strategy that is widely adopted in adjuvant research. Less well studied is how covalently linking different PAMPs affects the immune response. Herein, we summarise the research on the effect of PAMP linkage on innate and adaptive immune responses. These covalently linked or “chimeric” PAMPs often lead to immune cell synergies that are greater than those exhibited by the admixed (unconjugated) PAMPs, with several PAMP conjugates exhibiting remarkable adjuvant activity in a variety of disease contexts that include infectious disease, allergy, and cancer immunotherapy. This improvement in immune cell activation is thought to be due to more effective crosstalk between the different PRR signalling pathways, as conjugation ensures that each cell receives each class of PAMP. In addition, PAMP conjugates can form particulates, which has been postulated to lead to improved adjuvanticity, or they may facilitate the targeting of endosomal PRRs via the PRR-mediated endocytosis of the alternative PAMP in the conjugate. PAMP conjugates can also reduce the toxicity of individual PAMPs. However, not all PAMP conjugates are effective, and there are still many aspects of this research platform that are poorly understood, including how linker chemistry affects the immune response and how PRR signalling pathways or PAMP combinations combine to skew the immune response. We will address these and other outstanding questions that relate to the use of PAMP conjugates as vaccine adjuvants. Full article

(This article belongs to the Special Issue Novel Vaccine Designs to Enhance the Engagement of Innate and Adaptive Immunity)

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19 pages, 2698 KB

Open AccessArticle

Post-Marketing Safety of mRNA Vaccines: A Real-World Study Integrating Literature Case Reports and Vaccine Adverse Event Reporting System

by Bagejiang Tulisibaike, Tian-Yi Yang, Wen-Jun Gu, Huan Liu, Yuan-Hui Wang, Jin-Qi Yang, Tong Wang, Si-Miao Ding, Rong-Xue Cai, Yuan-Jie Wang, Wei Wang, Hong-Xing Pan, Fang Shao and Yu-Wen Su

Vaccines 2026, 14(6), 524; https://doi.org/10.3390/vaccines14060524 - 12 Jun 2026

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Abstract

Background: mRNA vaccines, first approved in December 2020, have been used globally to prevent infectious diseases, and those for treating cancers are being developed. Safety-related labelling changes of Comirnaty and Spikevax were made in June 2025; however, concerns remain. This study assessed [...] Read more.

Background: mRNA vaccines, first approved in December 2020, have been used globally to prevent infectious diseases, and those for treating cancers are being developed. Safety-related labelling changes of Comirnaty and Spikevax were made in June 2025; however, concerns remain. This study assessed the potential risks associated with mRNA vaccines on the indications previously approved, utilizing Real-World Data (RWD) of Adverse Events Following Immunization (AEFIs) derived from the Vaccine Adverse Event Reporting System (VAERS) and Academic Literature Databases (ALD). Methods: A Disproportionality Analysis (DPA) was performed using the Reporting Odds Ratio (ROR) and the Bayesian Confidence Propagation Neural Network (BCPNN) algorithm on spontaneous case reports from VAERS. Statistical positive signals were cross-validated with literature case reports from ALD to provide more comprehensive medical descriptions and clearer causal assessments, and compared with safety information documented in clinical trials and on vaccine labelling. Time-to-onset, stratified, and immunization schedule analyses were conducted to characterize the safety profiles of mRNA vaccines. Results: In total, 5,040,725 spontaneous case reports and 4,387 literature case reports were analyzed. In both VAERS and ALD, new signals involving blood and lymphatic system disorders (e.g., thrombotic thrombocytopenic purpura) and ear and labyrinth disorders (e.g., deafness) were detected from Comirnaty as Designated Medical Events (DMEs), while blood and lymphatic system disorders (e.g., thrombotic thrombocytopenic purpura) from Spikevax in ALD only. No new signals were detected from other vaccines on the DMEs list. In VAERS, Serious Adverse Events (SAEs) were more common in females, while death risk was higher in males. In ALD, SAEs were more common in males for most mRNA vaccines, except Comirnaty. Medical history emerged as a key risk factor for SAEs, particularly among older adults. Conclusions: Statistically significant safety signals were detected across all mRNA vaccines based on five-year cumulative RWD, indicating the need of intensified monitoring of specific populations, including older adults and individuals with medical histories, alongside further optimization of vaccination strategies. Full article

(This article belongs to the Special Issue mRNA Vaccines in Disease Prevention and Treatment)

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17 pages, 856 KB

Open AccessArticle

Larger Acute Phase Reactions Are Associated with Immunogenicity of an Adjuvanted Recombinant Receptor Binding Domain Protein Vaccine Against SARS-CoV-2 in Rhesus Monkeys

by Christopher L. Coe, Gabriele R. Lubach, Francesca Nimityongskul, Kimberly Luke, Eva G. Rakasz, David M. Rancour and Fritz M. Schomburg

Vaccines 2026, 14(6), 523; https://doi.org/10.3390/vaccines14060523 - 11 Jun 2026

Viewed by 364

Abstract

Background: Although prolonged inflammatory symptoms are an infrequent and problematic adverse effect of vaccination that can occur in some people, the transient activation of acute phase reactants (APRs) is expected with adjuvanted vaccines and helps to potentiate immune responses. Methods: This experiment examined [...] Read more.

Background: Although prolonged inflammatory symptoms are an infrequent and problematic adverse effect of vaccination that can occur in some people, the transient activation of acute phase reactants (APRs) is expected with adjuvanted vaccines and helps to potentiate immune responses. Methods: This experiment examined the association between vaccine reactogenicity and immunogenicity in monkeys immunized with an adjuvanted recombinant protein including a receptor binding domain–human IgG1-Fc fusion protein (RBD-Fc) sequenced from the ancestral Wuhan strain of SARS-CoV-2. The acute inflammatory reaction to immunization was assessed by determining the decline in serum iron levels at 24 h and the increase in the neutrophil-to-lymphocyte ratio (NLR) as the adherent neutrophil pool trafficked into circulation. Results: Robust primary and secondary antibody responses were elicited. Larger decreases in serum iron and higher NLRs were associated with a stronger inhibition of RBD binding with angiotensin-converting enzyme (ACE2) when five early viral variants of SARS-CoV-2 were tested, including Wuhan, Alpha, Beta, Gamma and Delta. Inhibition of ACE2-RBD binding was less evident when the Omicron variant was tested. Individual variation in the APR was also predictive of the persistence of cell-mediated immunity based on the number of interferon-expressing mononuclear cells activated by viral antigen in ELISpot assays. Conclusions: Rapid antibody responses to primary immunization and large secondary responses to booster immunizations were elicited by this adjuvanted recombinant RBD-Fc vaccine, and our analysis affirmed the view that a transient APR can enhance antibody binding with antigen proteins. Full article

(This article belongs to the Special Issue Research on Immune Response and Vaccines: 2nd Edition)

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33 pages, 1836 KB

Open AccessArticle

Influenza Vaccine Technology Transfer: A Mixed-Methods Study with Vaccine Manufacturers and Global Experts to Assess Successes, Challenges, and Opportunities

by Christopher Chadwick, Erin Sparrow, Claudia Nannei, Jessica Taaffe, William Ampofo, Antoine Flahault and Seth Berkley

Vaccines 2026, 14(6), 522; https://doi.org/10.3390/vaccines14060522 - 11 Jun 2026

Viewed by 447

Abstract

Background/Objectives: Technology transfer (TT) has been identified as a global health priority due to its impact on improving access to vaccines, including for pandemic influenza preparedness and response through bilateral and multilateral mechanisms. This study aimed to (1) characterize examples of influenza vaccine [...] Read more.

Background/Objectives: Technology transfer (TT) has been identified as a global health priority due to its impact on improving access to vaccines, including for pandemic influenza preparedness and response through bilateral and multilateral mechanisms. This study aimed to (1) characterize examples of influenza vaccine TT (IVTT) and (2) identify key lessons learned that may inform future activities relevant for next-generation influenza vaccine technologies. Methods: Using a contingent effectiveness model, a convergent mixed-methods study was conducted with vaccine manufacturers and global experts to capture quantitative survey data on IVTT activities and enablers and qualitative data on successes, challenges, and opportunities for IVTT through interviews, complemented by secondary data from peer-reviewed and grey literature to characterize additional IVTT observations. Results: This study included 24 participants, including 14 representatives from 13 vaccine manufacturers and 10 experts. Interviews were conducted with representatives from eight manufacturers and seven experts. Eighteen IVTT observations were identified through the surveys and interviews, of which 15 IVTT transfers were completed and 13 resulted in an approved vaccine. Secondary data provided additional evidence on eight IVTT recipients and one supplier, expanding the range of institutional and programmatic contexts assessed. Shorter IVTT completion and vaccine approval timelines were observed in association with prior TT experience and private management structures for manufacturers, for pre-pandemic/pandemic influenza vaccines versus seasonal influenza vaccines, and among bilateral transfer mechanisms (versus multilateral mechanisms) and fill/finish transfer methods. Manufacturers also described spillover benefits, including the use of IVTT-related know-how for the development of COVID-19 and routine vaccines. Both manufacturers and experts generally agreed on a list of 17 enablers for successful IVTT and ranked government commitment to vaccine production and procurement as the top enabler. Findings from the literature-based observations were consistent with primary data and included additional public sector recipient experiences, evidence of widespread human capital development, and a commentary on the importance of the demand environment. Conclusions: Assessed IVTT activities across primary and secondary data sources yielded commercial and spillover benefits as described in the contingent effectiveness model and provided a triangulated analysis of IVTT experiences across manufacturers, experts, and documented cases. Participants agreed that effective technology transfer is contingent upon a host of determinants. Using a systematic application of the contingent effectiveness model to IVTT, this study provided an exploratory analysis of past activities among vaccine manufacturers and experts. While certain nuances for influenza were identified, the lessons learned from this study may be applicable for other TT activities, including those to support pandemic preparedness. The contingent effectiveness model is a useful tool to inform and evaluate future TT activities. Full article

(This article belongs to the Special Issue Pandemic Influenza Vaccination)

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