Vaccines

17 pages, 839 KB

Open AccessArticle

A Randomized, Double-Blind, Placebo-Controlled Phase I Study to Evaluate the Safety, Tolerability, and Immunogenicity of an Outer Membrane Vesicle (OMV) Platform-Based Vaccine Administered Intranasally to Healthy Adults

by Heleen Kraan, Anne van der Geest, Dinja Oosterhoff, Corine Kruiswijk and Peter Soema

Vaccines 2026, 14(7), 575; https://doi.org/10.3390/vaccines14070575 (registering DOI) - 29 Jun 2026

Abstract

Background: The COVID-19 pandemic exposed critical gaps in pandemic preparedness and highlighted the need for vaccine platforms capable of rapid adaptation. Outer membrane vesicle (OMV)-based platforms utilizing vesicles derived from genetically detoxified Neisseria meningitidis serogroup B (Nm-nOMV) represent a promising plug-and-play approach. Methods: [...] Read more.

Background: The COVID-19 pandemic exposed critical gaps in pandemic preparedness and highlighted the need for vaccine platforms capable of rapid adaptation. Outer membrane vesicle (OMV)-based platforms utilizing vesicles derived from genetically detoxified Neisseria meningitidis serogroup B (Nm-nOMV) represent a promising plug-and-play approach. Methods: This Phase I, first-in-human, randomized, double-blind, placebo- and OMV-controlled trial, evaluated safety, tolerability, and immunogenicity of intranasally administered OMVs combined with SARS-CoV-2 Spike protein in healthy SARS-CoV-2 seropositive adults aged 18–55 years. Forty participants were enrolled across two cohorts: a low-dose cohort receiving 140 μg OMV/70 μg Spike (OMV + Spike, n = 13; OMV alone, n= 3; Placebo, n = 5) and a high-dose cohort receiving 280 μg of OMV/140 μg of Spike (OMV + Spike, n = 13; OMV alone, n = 3; Placebo, n = 3), administered on Days 1 and 22. Safety was assessed through adverse events, vital signs, laboratory parameters, ECG, and pulse oximetry. Immunogenicity was evaluated via systemic SARS-CoV-2 neutralizing antibodies, antigen-specific antibodies (IgG and IgA), and mucosal antibodies (IgA in nasal wash). Results: Intranasal administration of OMVs combined with SARS-CoV-2 Spike protein was safe, well-tolerated, and immunogenic. No serious adverse events were reported, and adverse events were predominantly mild and transient. Dose-dependent increases in systemic and mucosal immune responses were observed, with statistically significant enhanced serum IgG and nasal wash IgA antibodies in the high-dose group. Conclusions: The current clinical data confirm key aspects of the preclinical profile, which demonstrate the potential of the Nm-nOMV platform as a strong adjuvant for mucosal vaccines. These findings support the broader application of the Nm-nOMV vaccine platform in pandemic preparedness. Full article

(This article belongs to the Section Vaccine Design, Development, and Delivery)

34 pages, 2609 KB

Open AccessReview

Influenza B Vaccines: Current Landscape and Novel Development Strategies

by Roman Y. Kotlyarov, Nikolai V. Ravin and Eugenia S. Mardanova

Vaccines 2026, 14(7), 574; https://doi.org/10.3390/vaccines14070574 (registering DOI) - 29 Jun 2026

Abstract

Influenza B virus (IBV) represents a significant global health threat, contributing 20–30% of annual influenza cases and causing substantial morbidity and mortality across all age groups. Current seasonal vaccines demonstrate variable effectiveness, highlighting the urgent need for next-generation approaches that provide enhanced and [...] Read more.

Influenza B virus (IBV) represents a significant global health threat, contributing 20–30% of annual influenza cases and causing substantial morbidity and mortality across all age groups. Current seasonal vaccines demonstrate variable effectiveness, highlighting the urgent need for next-generation approaches that provide enhanced and sustained protection against both IBV lineages. Moreover, continuous antigenic drift of circulating viruses progressively reduces the match between vaccine-induced antibodies and contemporary strains, necessitating broad-spectrum protection strategies. This review discusses influenza B virus control strategies, encompassing both conventional approaches and emerging vaccine technologies. While antiviral therapy, epidemiological surveillance, diagnostics, and non-pharmaceutical public-health measures are integral components of influenza B control, the present review focuses specifically on vaccine-based strategies. By critically appraising the available evidence, this review evaluates the extent to which these strategies may improve the effectiveness of IBV vaccines and, in the longer term, inform the prospect of reducing the burden of—or potentially eliminating—influenza B virus, a goal that remains hypothetical and requires clinical validation. Full article

(This article belongs to the Section Influenza Virus Vaccines)

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24 pages, 20288 KB

Open AccessArticle

Development of DuoChol, a Thermostable Inactivated Whole-Cell/B-Subunit Oral Cholera Vaccine in Enteric Capsule

by Manuela Terrinoni, Michael R. Lebens, Stefan L. Nordqvist, Frida Nilsson, Madeleine Löfstrand, Julia Lynch and Jan Holmgren

Vaccines 2026, 14(7), 573; https://doi.org/10.3390/vaccines14070573 (registering DOI) - 29 Jun 2026

Abstract

Background/Objectives: Cholera remains an important global health problem. Inactivated oral cholera vaccines (OCVs) are essential in the WHO/GTFCC (World Health Organization)/Global Task Force on Cholera Control strategy to end cholera by 2030; however, global supply is insufficient, they require partial cold-chain storage, [...] Read more.

Background/Objectives: Cholera remains an important global health problem. Inactivated oral cholera vaccines (OCVs) are essential in the WHO/GTFCC (World Health Organization)/Global Task Force on Cholera Control strategy to end cholera by 2030; however, global supply is insufficient, they require partial cold-chain storage, and their formulation and antigen contents leave room for improvement. We describe here the development and preclinical evaluation of DuoChol OCV, a next-generation thermostable oral vaccine designed to address these gaps. Methods: DuoChol is a lyophilized dry-powder formulation in enteric capsules containing formalin-inactivated Vibrio cholerae O1 El Tor Ogawa and Inaba isogenic bacteria, recombinant cholera toxin B subunit (rCTB), and sucrose as stabilizer. Methods describe the construction of the novel vaccine strains, processes for the preparation and characterization of vaccine components, and the final dry formulation in enteric capsules, and in vitro and in vivo vaccine stability analyses. Results: The newly engineered vaccine strains, together with a high-yield mixed-mode chromatography process for rCTB purification, enabled efficient and cost-effective vaccine production. Stability studies demonstrated complete preservation of O1 LPS and rCTB antigens for at least 21 months across temperatures of 4–40 °C. Moreover, regardless of storage duration or temperature, oral immunization of mice with DuoChol elicited strong serum and mucosal antibacterial and antitoxin responses that were similar to those induced by the licensed Dukoral^® OCV. Conclusions: Its heat stability, practical enteric capsule formulation, and potential for improved efficacy compared to inactivated whole-cell only OCVs support positioning DuoChol as a promising next-generation OCV, suitable for national cholera control programs and particularly advantageous for outbreak response, where rapid deployment and early, robust protection are essential. Full article

(This article belongs to the Section Vaccine Design, Development, and Delivery)

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30 pages, 979 KB

Open AccessArticle

Assessing Geographic Inequalities in Childhood Immunisation Coverage: A Critical Scoping Review of Spatial Analysis Methods

by Adrien Allorant, Nicole Bergen, M. Carolina Danovaro-Holliday, Joshua Lorin, Gustavo Caetano Corrêa, Danielle Boyda, Johanna Lee Belanger, Ravi Shankar Santhana Gopala Krishnan, Rocco Panciera and Ahmad Reza Hosseinpoor

Vaccines 2026, 14(7), 572; https://doi.org/10.3390/vaccines14070572 (registering DOI) - 29 Jun 2026

Abstract

Background: Spatial analysis methods, including model-based geostatistics (MBG), small-area estimation (SAE), and cluster detection, are increasingly used to map subnational immunisation coverage and identify geographic inequalities in low- and middle-income countries. However, the extent to which these methods capture the multidimensional determinants of [...] Read more.

Background: Spatial analysis methods, including model-based geostatistics (MBG), small-area estimation (SAE), and cluster detection, are increasingly used to map subnational immunisation coverage and identify geographic inequalities in low- and middle-income countries. However, the extent to which these methods capture the multidimensional determinants of immunisation uptake, and whether their outputs inform programme decisions in practice, remains unclear. Methods: We conducted a critical scoping review following the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews guidelines, systematically searching PubMed and Google Scholar for studies applying spatial statistical methods to childhood immunisation coverage or equity. Findings were synthesised using a combination of descriptive summary and thematic and interpretive synthesis. Results: We included 50 studies from the 421 papers identified. Spatial methods have successfully revealed subnational coverage inequalities that national averages obscure, and studies developed in collaboration with national programme teams, integrating routine health system data alongside household surveys, produced the most operationally relevant outputs. However, most studies relied exclusively on survey data with a limited incorporation of supply-side determinants, and few discussed how uncertainty in estimates should constrain downstream use. Although a growing number of studies articulated clear implementation pathways, confirmed programmatic uptake of spatial outputs remained largely undocumented. The emergence of machine learning approaches (8 of 50 studies) offers predictive gains but introduces additional challenges around transparency and quality assurance for governance use. Conclusions: Spatial methods are becoming more frequently used for immunisation but are more likely to contribute to immunisation equity goals when co-produced with programme teams, matched to decision-relevant geographies, and accompanied by transparent documentation of model assumptions and limitations. Future research should prioritise quality frameworks for algorithm-assisted health estimates and systematic evaluation of whether spatial outputs improve decision-making relative to existing data sources. Full article

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24 pages, 1738 KB

Open AccessReview

Arming Inactivated Enveloped Virus Vaccines with the GGTA1 Gene: A Potent Method for Amplification of Viral Vaccines Effectiveness and Protection Against Variants

by Uri Galili

Vaccines 2026, 14(7), 571; https://doi.org/10.3390/vaccines14070571 (registering DOI) - 29 Jun 2026

Abstract

This review describes a novel method for increasing the effectiveness of inactivated enveloped whole-virus vaccines by targeting them for extensive uptake by antigen-presenting cells (APCs). Several inactivated whole-virus vaccines with dense glycan shields display suboptimal effectiveness because the multiple carbohydrate chains (glycans) on [...] Read more.

This review describes a novel method for increasing the effectiveness of inactivated enveloped whole-virus vaccines by targeting them for extensive uptake by antigen-presenting cells (APCs). Several inactivated whole-virus vaccines with dense glycan shields display suboptimal effectiveness because the multiple carbohydrate chains (glycans) on the virus mask immunogenic peptides and surround the virus with a negative electrostatic charge that decreases uptake by APCs. It is postulated that engineering such vaccinating viruses to present the carbohydrate antigen “α-gal epitope” on the glycan shields will immunocomplex them with the anti-Gal antibody; thus, it will target them for robust uptake by APCs. Anti-Gal is an abundant natural antibody in humans, constituting ~1% of human circulating immunoglobulins. The ligand of anti-Gal is the α-gal epitope, which is naturally synthesized in non-primate mammals and New World monkeys by the glycosylation enzyme α1,3galactosyltransferase. This enzyme is encoded by the GGTA1-gene. Viral vaccines presenting multiple α-gal epitopes on their glycan shield bind anti-Gal and activate the complement system to produce complement chemotactic cleavage peptides C5a and C3a that induce extensive recruitment of APCs to vaccine injection sites. The virion-bound anti-Gal further targets the viral vaccine for robust uptake by APCs, following binding of its Fc “tail” to Fcγ-receptors on APCs. The efficacy of this method was studied in anti-Gal-producing mice with α-gal presenting inactivated influenza virus vaccine and with gp120 of HIV presenting this epitope. These studies indicated that virus vaccines engineered to present α-gal epitopes increase anti-virus antibody production and virus-specific T-cell activation by 15- to 100-fold in comparison to the same vaccines lacking α-gal epitopes. It is suggested that α-gal presenting inactivated SARS-CoV-2 virus vaccines can induce a similar protective long-term immune memory against S- M-, E-, and N-viral proteins. Furthermore, immune-escaping variants of the mutated S-protein may be destroyed by antibodies to M and E proteins, and cells infected with such variants may be killed by cytotoxic T cells specific to peptides of the N-protein. Such an anti-M-, E-, and N-protein immune protection may prevent expansion of these variants and thus may avoid the need for immunization with COVID-19 vaccines every 6 months or following the appearance of new variants. A similar potent immunization may be achieved with an inactivated Ebolavirus vaccine engineered to present α-gal epitopes on the glycan shield. The resulting immune response to the various Ebolavirus proteins also may contribute to cross-reactive protection against other Ebolavirus species containing proteins with evolutionarily conserved structures. An effective method for the preparation of a whole-virus vaccine presenting α-gal epitopes is by arming it with the GGTA1-gene inserted into the viral genome. Such virions will present multiple α-gal epitopes on their glycan shield, which will amplify their immunogenicity instead of reducing it in the wild-type virus. Full article

(This article belongs to the Section Vaccine Advancement, Efficacy and Safety)

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15 pages, 2794 KB

Open AccessArticle

Adult Seroprotection Gaps Against Diphtheria and Tetanus in Urban China: Repeated Cross-Sectional Serosurveillance in Pudong, Shanghai, 2017–2025

by Wanran Cheng, Juan Li, Tian Yang, Yu Bai, Pengfei Deng, Laibao Yang and Yihan Lu

Vaccines 2026, 14(7), 570; https://doi.org/10.3390/vaccines14070570 (registering DOI) - 29 Jun 2026

Abstract

Background: Adult susceptibility to diphtheria and tetanus may increase as vaccine-induced immunity wanes, yet repeated population-based serosurveillance data in China are limited. Methods: We analyzed annual serosurveys conducted in Pudong New Area, Shanghai, China, from 2017 to 2025 among healthy adults [...] Read more.

Background: Adult susceptibility to diphtheria and tetanus may increase as vaccine-induced immunity wanes, yet repeated population-based serosurveillance data in China are limited. Methods: We analyzed annual serosurveys conducted in Pudong New Area, Shanghai, China, from 2017 to 2025 among healthy adults aged 20–49 years. Diphtheria and tetanus IgG concentrations were measured by ELISA. Seroprotection was defined as antibody concentration ≥0.1 IU/mL. Antibody concentrations were further categorized as <0.01, 0.01–<0.1, 0.1–<1.0, and ≥1.0 IU/mL, and geometric mean concentrations (GMCs) were calculated. Multivariable logistic regression models were fitted to assess factors associated with non-protection, including survey year, age group, and household registration. Sensitivity analyses excluding the 2018 survey year were conducted. Results: A total of 2376 serum samples were included. Overall seroprotection was 21.46% for diphtheria and 13.80% for tetanus. The proportion protected against both antigens was 9.05%, while 73.78% showed concurrent non-protection against both antigens. The overall GMC was 0.032 IU/mL (95% CI: 0.030–0.034) for diphtheria and 0.018 IU/mL (95% CI: 0.017–0.019) for tetanus. Concentrations ≥1.0 IU/mL were uncommon for both antigens. Adults aged 40–49 years had higher odds of non-protection than those aged 20–29 years for diphtheria (OR: 2.43, 95% CI: 1.85–3.21) and tetanus (OR: 2.94, 95% CI: 2.11–4.13). Non-local residents also had higher odds of non-protection than local residents for diphtheria (OR: 1.55, 95% CI: 1.24–1.93) and tetanus (OR: 2.81, 95% CI: 2.15–3.69). Seroprotection varied across survey years, with a marked nadir in 2018. Sensitivity analyses excluding 2018 attenuated most year-specific associations, whereas age- and residence-related differences persisted. Conclusions: Healthy adults aged 20–49 years in Pudong showed low seroprotection and low GMCs against both diphtheria and tetanus, with a high proportion concurrently non-protected against both antigens. These findings highlight a persistent adult immunity gap and support further evaluation of adult booster strategies and enhanced serosurveillance. Full article

(This article belongs to the Special Issue Preventing Outbreak Through Vaccination)

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15 pages, 227 KB

Open AccessArticle

Family Vaccination Context Predicts HPV Vaccine Uptake Among Medical Students

by Farah Harb, Shakhnozakhon Mukhtorova, Akarsh Lal, Laila Al-Jerdi, Morhaf Al Achkar and Radhika Gogoi

Vaccines 2026, 14(7), 569; https://doi.org/10.3390/vaccines14070569 (registering DOI) - 28 Jun 2026

Abstract

Background/Objectives: Human papillomavirus (HPV) vaccination is an important cancer prevention strategy, yet uptake remains incomplete. Although provider recommendation is a key driver of HPV vaccination, less is known about how future physicians’ own vaccination behaviors are shaped. This study examined whether family vaccination [...] Read more.

Background/Objectives: Human papillomavirus (HPV) vaccination is an important cancer prevention strategy, yet uptake remains incomplete. Although provider recommendation is a key driver of HPV vaccination, less is known about how future physicians’ own vaccination behaviors are shaped. This study examined whether family vaccination context was associated with HPV vaccine uptake among medical students, with attention to implications for future vaccine counseling and prevention training. Materials and Methods: We conducted a cross-sectional analysis of survey data from 230 medical students at Wayne State University School of Medicine. The primary outcome was self-reported HPV vaccination status, dichotomized as fully vaccinated versus not fully vaccinated or unsure. Predictors included family vaccination context, gender, religious affiliation, age, year in medical school, prior HPV education, HPV knowledge, and HPV stigma. Family vaccination context was modeled as an ordinal predictor based on agreement that family members of age were vaccinated. HPV knowledge was modeled using a 22-item baseline pre-survey composite score. HPV stigma was modeled as a 2-item composite assessing perceived stigma associated with HPV and disclosure. Analyses included univariate and bivariate tests, followed by complete-case multivariable logistic regression. A sensitivity analysis restricted the outcome to vaccinated versus unvaccinated students, excluding those who were unsure. Results: Of 230 students, 189 (82.2%) reported being fully vaccinated against HPV. In bivariate analyses, family vaccination context, gender, and HPV knowledge were associated with vaccination status, whereas religion, age, year in medical school, prior HPV education, and HPV stigma were not. In the adjusted model (n = 165), family vaccination context remained the strongest independent correlate of HPV vaccination status (OR, 3.95; 95% CI, 2.11–7.42; p < 0.001). Female gender was also associated with higher odds of vaccination (OR, 3.80; 95% CI, 1.01–14.29; p = 0.048), as was higher HPV knowledge (OR, 1.26; 95% CI, 1.03–1.53; p = 0.024). HPV stigma showed a borderline inverse association with vaccination status (OR, 0.53; 95% CI, 0.26–1.07; p = 0.076). Religion, age, year in medical school, and prior HPV education were not statistically significant after adjustment. The family vaccination association remained robust in the vaccinated-versus-unvaccinated sensitivity analysis (OR, 7.70; 95% CI, 2.45–24.26; p < 0.001). Exploratory secondary analyses suggested that family vaccination context may also be associated with stronger intention to recommend HPV vaccination to future patients and greater intent to vaccinate among students who were not fully vaccinated or unsure, although these findings should be interpreted cautiously. Conclusions: Perceived family vaccination context was the strongest and most consistent correlate of self-reported HPV vaccine completion among medical students in this cross-sectional study. Gender and HPV knowledge were also associated with vaccination status in the primary adjusted model, although these estimates were less precise and less consistent across model specifications. Findings should be interpreted as associations rather than causal effects. HPV prevention training may benefit from addressing not only factual knowledge, but also trainees’ vaccination histories, perceived family and social norms, HPV-related stigma, and comfort discussing vaccination as part of preparation for future cancer prevention counseling. Full article

(This article belongs to the Special Issue Improving HPV Vaccination Coverage: Current Challenges, Emerging Strategies and Future Directions: 2nd Edition)

12 pages, 11251 KB

Open AccessArticle

Rationally Modified SARS-CoV-2 Spike Protein Impairs ACE2 Binding While Preserving Immunogenicity in Mice

by Elia Tamagnini, Luca Simonelli, Martin Palus, Tanja Rezzonico Jost, Edoardo Lazzarini, Davide Mangani, Václav Hönig, Markéta Dvořáková, Dominik Arbon, Federica Gambini, Sara Lestani, Fabio Grassi, Lucio Barile, Mattia Pedotti, Radislav Sedlacek and Luca Varani

Vaccines 2026, 14(7), 568; https://doi.org/10.3390/vaccines14070568 (registering DOI) - 27 Jun 2026

Abstract

Background: While vaccines are designed to elicit targeted immune responses, in some cases, the immunogenic molecules employed can inherently interact with broader host cellular pathways as a secondary consequence. This phenomenon can be exemplified by COVID-19 vaccines. COVID-19 vaccines, including mRNA platforms, use [...] Read more.

Background: While vaccines are designed to elicit targeted immune responses, in some cases, the immunogenic molecules employed can inherently interact with broader host cellular pathways as a secondary consequence. This phenomenon can be exemplified by COVID-19 vaccines. COVID-19 vaccines, including mRNA platforms, use the SARS-CoV-2 spike protein as an immunogen to induce the production of neutralizing antibodies. The spike protein binds the ACE2 (angiotensin-converting enzyme 2) receptor on human cells, mediating viral entry and infection. ACE2 is widely expressed across multiple tissues and is a key component of the renin–angiotensin–aldosterone system (RAAS) that acts as a homeostatic regulator of systemic and local blood flow, blood pressure, cardiac function, fluid balance and immunity. Some studies have proposed the interaction between the spike protein and ACE2 as a possible contributing factor to rare adverse effects observed following COVID-19 vaccination, including myocarditis, pericarditis, thrombosis, and reported alterations in blood pressure, though these mechanisms remain to be fully elucidated. Objectives: As a proof-of-concept approach in vaccine antigen development, we engineered SARS-CoV-2 spike mutants with impaired binding to the host receptor ACE2. Methods: By rational design, we produced and validated in vitro and in vivo spike point mutants that do not effectively bind ACE2. Results: The engineered spike mutants do not effectively bind the human entry receptor ACE2 while retaining the immunogenic properties equal to or better than the wild type spike and thus generate a protective response in animals when used as a vaccination agent. Conclusions: By establishing a straightforward molecular strategy for rational vaccine design, this work demonstrates the feasibility of limiting specific antigen–host receptor interactions while maintaining immunogenicity. This approach may be applicable to future vaccination strategies where antigen interaction with host cells could potentially interfere with physiological pathways. Full article

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

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22 pages, 810 KB

Open AccessReview

Zinc: An Emerging Axis of Host–Pathogen Interaction in Tuberculosis

by Jordan Holl, Jamie Corro, Bibhuti B. Mishra and Anil K. Ojha

Vaccines 2026, 14(7), 567; https://doi.org/10.3390/vaccines14070567 (registering DOI) - 27 Jun 2026

Abstract

Zinc is an essential micronutrient required by all forms of life, including Mycobacterium tuberculosis (Mtb), the etiological agent of tuberculosis. Mtb can persist within the host for years and requires a prolonged, multidrug treatment regimen for effective clearance. The sequestration of essential metals, [...] Read more.

Zinc is an essential micronutrient required by all forms of life, including Mycobacterium tuberculosis (Mtb), the etiological agent of tuberculosis. Mtb can persist within the host for years and requires a prolonged, multidrug treatment regimen for effective clearance. The sequestration of essential metals, including zinc, during bacterial infection is a key component of the host’s innate immune response. In this process, metal-chelating proteins such as the neutrophil-derived protein, calprotectin, play a central role in nutritional immunity by limiting microbial access to critical metal cofactors. Despite its importance, the impact of nutritional immunity on Mtb pathogenesis remains incompletely understood. In this review, we summarize recent advances in our understanding of zinc-responsive adaptations in Mtb and propose that zinc limitation within the host contributes significantly to the long-term persistence of this pathogen. Full article

(This article belongs to the Special Issue Immunobiology of Mycobacterium tuberculosis and Its Implication in Vaccine Design)

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14 pages, 981 KB

Open AccessArticle

Evaluation of Hepatitis B Vaccine Immunogenicity in Low-Birth-Weight Infants After Complete Immunization: The Impact of Postnatal Catch-Up Growth and Maternal–Neonatal Characteristics

by Lu Shen, Wanqin Tang, Yan Xie, Ran Hu, Jintao Wang, Yunke Qian, Huaxian Liu, Yang Yu and Zhongkui Zhu

Vaccines 2026, 14(7), 566; https://doi.org/10.3390/vaccines14070566 (registering DOI) - 27 Jun 2026

Abstract

Background: Low-birth-weight (LBW, <2500 g) infants are at increased risk of suboptimal hepatitis B vaccine responses; yet, data on their immunogenicity patterns and modifiable determinants remain limited. This study aimed to assess hepatitis B vaccine immunogenicity in LBW infants and to examine [...] Read more.

Background: Low-birth-weight (LBW, <2500 g) infants are at increased risk of suboptimal hepatitis B vaccine responses; yet, data on their immunogenicity patterns and modifiable determinants remain limited. This study aimed to assess hepatitis B vaccine immunogenicity in LBW infants and to examine whether postnatal catch-up growth and maternal–neonatal characteristics are independently associated with antibody levels. Methods: We enrolled 511 LBW infants who completed the recommended 3-dose hepatitis B vaccination series at 0, 1, and 6 months. Blood samples were collected 4–6 weeks after completion of the full vaccination series. Geometric mean concentration (GMC) and seroprotection rate (SPR, anti-HBs ≥ 10 mIU/mL) were evaluated. Catch-up growth was quantified as the change in weight-for-age Z-score between 6 and 8 months of age (ΔWAZ). Multivariable linear regression was used to identify independent predictors of log-transformed antibody titers, adjusting for gestational age, maternal hepatitis B surface antigen (HBsAg) positivity, maternal body mass index (BMI), maternal fasting glucose, maternal thyroid disease, infant hemoglobin at 6 months, and ΔWAZ. Results: The overall SPR was 99.41% (508/511), with a GMC of 1045.37 mIU/mL (95% CI: 916.24–1192.70). SPR remained consistently high across all subgroups. In multivariable analysis, ΔWAZ was not significantly associated with antibody levels (β = −0.063, p = 0.571). Maternal HBsAg positivity showed no significant association (β = −0.104, p = 0.792). Maternal thyroid disease was independently associated with higher antibody levels (β = 0.793, 95% CI: 0.213–1.373, p = 0.007). None of the other covariates reached statistical significance. Conclusions: Hepatitis B vaccination demonstrated high immunogenicity in LBW infants, with very high seroprotection rates. Postnatal catch-up growth did not independently influence antibody levels. The significant positive association between maternal thyroid disease and infant antibody response warrants further prospective investigation. Full article

(This article belongs to the Section Hepatitis Virus Vaccines)

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20 pages, 663 KB

Open AccessReview

Knowledge, Awareness, Attitudes, Acceptance, and Uptake of the Herpes Zoster Vaccine in Saudi Arabia: A Scoping Review

by Howeida Abusalih

Vaccines 2026, 14(7), 565; https://doi.org/10.3390/vaccines14070565 (registering DOI) - 26 Jun 2026

Abstract

Background: Herpes zoster (HZ), commonly known as shingles, and post-herpetic neuralgia (PHN) represent growing public health concerns, particularly among older adults. Despite the established efficacy of the herpes zoster vaccine (HZV), global uptake remains suboptimal. Objectives: This scoping review maps evidence [...] Read more.

Background: Herpes zoster (HZ), commonly known as shingles, and post-herpetic neuralgia (PHN) represent growing public health concerns, particularly among older adults. Despite the established efficacy of the herpes zoster vaccine (HZV), global uptake remains suboptimal. Objectives: This scoping review maps evidence from Saudi Arabia evaluating the baseline knowledge, awareness, attitudes, acceptance, hesitancy, and clinical uptake of the HZV among general adults, high-risk populations, and healthcare workers (HCWs). Methods: The JBI and PRISMA-ScR methodological frameworks were strictly adhered to during mapping. Eligible sources included peer-reviewed, observational cross-sectional studies conducted in Saudi Arabia and published in English between 2022 and 2026. The search was conducted across PubMed, Scopus, Web of Science, and Google Scholar. Data were systematically extracted and charted using a standardized digital piloting framework to capture study characteristics (author, year, and region), sample sizes, target populations, knowledge percentages, actual vaccine uptake rates, and self-reported barriers. Results: Out of 25 retrieved records, 19 unique primary studies were mapped. Public knowledge of HZ complications and vaccine eligibility criteria was consistently low to moderate, falling below 50% across most cohorts. Conversely, while verbal willingness to receive the vaccine was highly favorable (ranging from 60% to 75%), a profound “intention–behavior gap” was observed, with actual clinical uptake being below 10%. Key barriers included a lack of public health campaigns, safety concerns regarding reactogenicity, online misinformation, and a lack of proactive provider communication. For HCWs, barriers included unclear local guidelines and a lack of workplace mandates. Ultimately, a proactive physician recommendation was identified as the single most powerful clinical facilitator, increasing vaccine acceptance by over 80% across all cohorts. Conclusions: While the shingles vaccine is now distributed completely free across Saudi Arabia, high public willingness has not translated into actual vaccination rates (10%) due to low public awareness of disease severity. Free vaccine availability alone is insufficient; primary care systems must shift from a passive delivery model to an active, provider-driven framework to successfully close this gap Full article

(This article belongs to the Special Issue Vaccination and Public Health Strategy)

20 pages, 6819 KB

Open AccessArticle

Molecular Variation in Porcine Circovirus Type 2 in Jalisco, Mexico, and Its Potential Impact on Vaccine Efficacy

by Alberto Jorge Galindo-Barboza, José Francisco Rivera-Benítez, Jazmín De la Luz-Armendáriz, José Iván Sánchez-Betancourt, Jesús Hernández, Alexel Jesús Burgara-Estrella, Suzel Guadalupe Sauceda-Cerecer, Laura Márquez-Valdelamar and Jaime Enrique De Alba-Campos

Vaccines 2026, 14(7), 564; https://doi.org/10.3390/vaccines14070564 (registering DOI) - 26 Jun 2026

Abstract

Background/Objectives: Porcine circovirus type 2 (PCV2) remains a major viral agent in pig production worldwide due to its association with economically relevant diseases and productivity losses. Nine genotypes (PCV2a–PCV2i) have been reported, with successive genotype shifts characterized by the historical predominance of PCV2a, [...] Read more.

Background/Objectives: Porcine circovirus type 2 (PCV2) remains a major viral agent in pig production worldwide due to its association with economically relevant diseases and productivity losses. Nine genotypes (PCV2a–PCV2i) have been reported, with successive genotype shifts characterized by the historical predominance of PCV2a, the expansion of PCV2b, and the emergence of PCV2d as the predominant genotype in several swine-producing countries. The aim of this study was to characterize the ORF2 gene of PCV2 circulating in Jalisco, Mexico, to provide updated information for regional surveillance and control strategies. Methods: Samples were collected from 80 pig farms located in four regions of Jalisco with different pig density levels and production systems. PCV2-positive samples were subjected to ORF2 amplification and sequencing. Genotype assignment, phylogenetic analysis, and in silico recombination screening using multiple detection methods were performed. All sequences were deposited in GenBank. Results: A total of 70 ORF2-PCV2 sequences were obtained and assigned to two genotypes: PCV2d (51/70, 72.9%) and PCV2a (19/70, 27.1%). The sequences were submitted to GenBank under accession numbers PV235521–PV235590. Recombination analysis identified seven recombinant sequences, and unusual ORF2 extensions were detected in some sequences, evidencing the presence of genetic variants circulating in the region. Conclusions: These findings confirm the predominance of PCV2d in Jalisco while highlighting the continued circulation of PCV2a. The coexistence of both genotypes, together with recombinant sequences and ORF2 extensions, indicates ongoing PCV2 genetic diversification in the region. Continuous molecular surveillance remains essential to monitor viral evolution, support genotype-informed control strategies, and strengthen swine health programs. Full article

(This article belongs to the Special Issue Animal Infectious Diseases and Vaccinology in One Health)

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27 pages, 1182 KB

Open AccessReview

Minicircle DNA Vaccines: Overcoming Delivery and Expression Barriers in Next-Generation Immunization

by Ibtihal S. Alduhaymi, Majed A. Majrashi, Ibrahim A. Alradwan, Faisal S. Alagrafi, Musaad A. Altammami, Ahmad M. Aldossary, Fahad A. Almughem, Abdullah A. Alshehri, Mohannad M. Fallatah, Nojoud Al Fayez and Essam A. Tawfik

Vaccines 2026, 14(7), 563; https://doi.org/10.3390/vaccines14070563 - 26 Jun 2026

Abstract

DNA vaccines have emerged as a promising immunization platform, offering key advantages over conventional vaccine approaches, including superior stability, a favorable safety profile, rapid and flexible antigen design, and scalable manufacturing. However, their clinical efficacy has remained limited, primarily due to inefficient cellular [...] Read more.

DNA vaccines have emerged as a promising immunization platform, offering key advantages over conventional vaccine approaches, including superior stability, a favorable safety profile, rapid and flexible antigen design, and scalable manufacturing. However, their clinical efficacy has remained limited, primarily due to inefficient cellular uptake, poor endosomal escape, and degradation of the plasmid DNA within host cells. Recent advances have highlighted minicircle DNA (mcDNA) as a next-generation alternative to conventional plasmid vectors. mcDNA constructs are compact, backbone-free episomal vectors containing only the expression cassette, including the promoter, transgene, and polyadenylation signal, while lacking bacterial sequences such as antibiotic resistance genes and origins of replication. This reduced vector size reduced vector-driven innate immune activation and susceptibility to epigenetic silencing, thereby improving transfection efficiency and supporting more sustained transgene expression in both dividing and non-dividing cells. This review provides a comprehensive overview of mcDNA technology in the context of vaccine development, discussing its structural design and production principles, mechanistic advantages over conventional plasmid DNA, and current applications across infectious disease and cancer vaccine platforms. In addition, we explore recent delivery strategies to enhance mcDNA transfection and immunogenicity, summarize existing limitations that hinder translation into applications, and outline future directions to optimize mcDNA-based vaccine technologies. Full article

(This article belongs to the Section Nucleic Acid (DNA and mRNA) Vaccines)

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16 pages, 271 KB

Open AccessReview

Cancer Vaccine Strategies in Non-Small Cell Lung Cancer

by Rogelio N. Velasco, Jr., Pragadeesh Thamaraiselvan, Edoardo Garbo, Silvia Novello and Francesco Passiglia

Vaccines 2026, 14(7), 562; https://doi.org/10.3390/vaccines14070562 - 25 Jun 2026

Abstract

Despite significant improvement in long-term survival with the advent of immunotherapy, a substantial proportion of lung cancer patients develop primary and acquired resistance. Among emerging strategies to overcome this challenge, cancer vaccines represent a promising approach, especially for non-small-cell lung cancer (NSCLC). A [...] Read more.

Despite significant improvement in long-term survival with the advent of immunotherapy, a substantial proportion of lung cancer patients develop primary and acquired resistance. Among emerging strategies to overcome this challenge, cancer vaccines represent a promising approach, especially for non-small-cell lung cancer (NSCLC). A variety of vaccine platforms have been investigated, including nucleic acid-based vaccines, peptide vaccines, dendritic cell vaccines, and viral vector-based approaches. To date, cancer vaccines have not demonstrated consistent survival benefit in large randomized trials, and their clinical application remains limited. Challenges include high production costs, complexity in manufacturing, and issues related to drug stability and scalability. However, several ongoing early-phase trials show promising signals for several platforms, as new tools and technology become available to optimize neoantigen selection, vaccine production, efficacy, and safety. In this review, we summarize the current evidence of vaccines in NSCLC treatment across different stages and therapeutic settings. Full article

(This article belongs to the Special Issue The Era of Vaccines: Advancing Tumor Immunology and Immunotherapy)

23 pages, 3710 KB

Open AccessArticle

A Repeated and Delayed Homologous Challenge Study Evaluating the Durability of Protection Induced by the Live Attenuated ASF Vaccine Candidate ASFV-G-ΔI177L/ΔLVR

by Xinghua Zheng, Yeonji Kim, Sun A. Choi, Su Jin Lee, Seung Pyo Shin, Se Young Lee, Wonjun Kim, Seong Cheol Moon, Yongwoo Shin, Do Soon Kim, Byung-chul Shin, Sua Choi, Ji-yun Sung, Garam Kim, Weonhwa Jheong and Jung Hyang Sur

Vaccines 2026, 14(7), 561; https://doi.org/10.3390/vaccines14070561 - 25 Jun 2026

Abstract

Background/Objectives: African swine fever (ASF) is a highly lethal disease of domestic pigs and wild suids that continues to cause substantial economic losses worldwide. Despite recent progress in live attenuated ASF vaccine development, evidence supporting durable protection under repeated exposure conditions representative of [...] Read more.

Background/Objectives: African swine fever (ASF) is a highly lethal disease of domestic pigs and wild suids that continues to cause substantial economic losses worldwide. Despite recent progress in live attenuated ASF vaccine development, evidence supporting durable protection under repeated exposure conditions representative of endemic settings remains limited. Here, we assessed the long-term safety and protective efficacy of a live attenuated ASFV-G-ΔI177L/ΔLVR vaccine using a repeated-challenge experimental design intended to model re-exposure in ASF-endemic regions. Methods: Vaccinated pigs were subjected to homologous virulent ASF virus challenges at multiple intervals, including repeated challenges (three sequential inoculations) and single challenges administered at 8 and 12 weeks post-vaccination. Results: Across all challenge regimens, vaccinated animals survived and remained clinically healthy, including those receiving three challenges, supporting sustained protection under repeated exposure pressure. Animals challenged at 8 or 12 weeks post-vaccination likewise exhibited complete survival, indicating maintained efficacy through at least 12 weeks. No vaccine-associated adverse clinical outcomes were detected over the study period, and post-challenge viral shedding was minimal. Conclusions: Overall, these data demonstrate that the candidate live attenuated ASF vaccine provides excellent protective efficacy and confers sustained protection against homologous ASF virus infection. This result is expected to be equally applicable under repeated exposure conditions in regions with unstable ASF biosecurity, making it a sufficiently promising model experiment for field application in ASF epidemic areas. However, this is still a vaccine variant, and further studies are planned to evaluate its genomic stability and transmissibility. Full article

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33 pages, 2569 KB

Open AccessReview

Emerging Viral Zoonoses: Epidemiology, Vaccination Strategies, and Implications for Global Public Health

by Julia Dulska, Marek Fol and Magdalena Druszczynska

Vaccines 2026, 14(7), 560; https://doi.org/10.3390/vaccines14070560 - 25 Jun 2026

Abstract

Background/Objectives: Emerging viral zoonoses represent a growing threat to global public health, with most newly emerging infectious diseases originating from animal reservoirs. Recent outbreaks of monkeypox, Ebola virus disease, Marburg virus disease, Rift Valley fever, and avian influenza highlight the capacity of [...] Read more.

Background/Objectives: Emerging viral zoonoses represent a growing threat to global public health, with most newly emerging infectious diseases originating from animal reservoirs. Recent outbreaks of monkeypox, Ebola virus disease, Marburg virus disease, Rift Valley fever, and avian influenza highlight the capacity of zoonotic viruses to cross species barriers, spread internationally, and generate substantial health, social, and economic consequences. This review examines the ecological, epidemiological, and biological determinants of viral zoonotic emergence and transmission, with particular emphasis on vaccination and outbreak prevention strategies. Methods: A structured narrative review was conducted using a predefined literature search strategy across major scientific databases. Peer-reviewed epidemiological, clinical, and public health publications published between January 2000 and February 2026 were screened and selected according to predefined relevance criteria. Results: The emergence of viral zoonoses is driven by complex interactions among animal reservoirs, environmental and climatic changes, human behavior, and viral adaptation. Although transmission pathways and clinical outcomes differ among pathogens, common determinants of spillover and outbreak amplification were identified. Current evidence supports the importance of integrated surveillance, genomic monitoring, vaccination strategies, and community engagement as key components of preparedness and response. Emerging preventive approaches targeting pathogen transmission, including transmission-blocking strategies and vector-associated microbiota interventions, may provide additional opportunities for disease control. Conclusions: Strengthening preparedness for emerging viral zoonoses requires coordinated One Health approaches integrating human, animal, and environmental health. Future priorities include the development of next-generation vaccines, expansion of digital and genomic surveillance systems, improved equitable access to vaccines, and innovative interventions aimed at reducing zoonotic spillover and interrupting pathogen transmission. Full article

(This article belongs to the Special Issue Communicable Diseases: New and Old Therapies and Preventive Strategies, 2nd Edition)

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22 pages, 1027 KB

Open AccessReview

A Double-Edged Sword: Breast Milk-Derived Maternal Antibodies and Infant Vaccine Responses: A Narrative Review

by Alexandra Mpakosi, Rafaela Anna Moutsopoulou, Stamatios Cholevas, Alexandra Lianou, Andriana Samata, Foteini Tziraki, Ioannis Vogiatzis, Vasileios Cholevas, Zoi Iliodromiti, Theodora Boutsikou, Nicoletta Iacovidou, Andreas G. Tsantes and Rozeta Sokou

Vaccines 2026, 14(7), 559; https://doi.org/10.3390/vaccines14070559 - 25 Jun 2026

Abstract

Neonatal defense against pathogens relies on maternal antibodies transferred both through the placenta (IgG) and through breast milk (primarily secretory IgA). Maternal IgG antibodies are transferred across the placenta to the fetus mainly via the neonatal Fc receptor (FcRn), which is expressed at [...] Read more.

Neonatal defense against pathogens relies on maternal antibodies transferred both through the placenta (IgG) and through breast milk (primarily secretory IgA). Maternal IgG antibodies are transferred across the placenta to the fetus mainly via the neonatal Fc receptor (FcRn), which is expressed at high levels in placental syncytiotrophoblasts, and results in the acquisition of maternal-fetal IgG. Transplacental transfer via the FcRn pathway can provide therapeutic proteins and protective antibodies following maternal vaccination. However, maternal IgG antibodies can bind to vaccine antigens such as measles, tetanus, and poliovirus, resulting in rapid clearance through FcgRIIB-mediated inhibition and inadequate B cell activation. In this way, they can inhibit de novo immune responses and significantly reduce vaccine response. On the other hand, the interference that breast milk-derived antibodies may have on vaccine-induced immunity is still largely unknown. Vaccination against influenza, pertussis, and COVID-19 during pregnancy or lactation has been shown to induce the production of protective, pathogen-specific, secretory IgA and IgG antibodies in breast milk. Conversely, studies found that breast milk-derived antibodies of vaccinated mothers reduced vaccine-induced immunity in breastfed infants by accelerating the clearance of vaccine antigen, resulting in reduced antigen availability and reduced plasma cell formation after vaccination. Additional factors in middle- and low-income countries, including environmental (increased microbiome diversity, environmental intestinal dysfunction, malnutrition, co-infections) and breastfeeding practices, may exacerbate the interference effect of maternal antibodies. Current evidence supports that breastfeeding is associated with a reduced immunological response exclusively to the rotavirus vaccine. However, the limited evidence base to date precludes definitive conclusions regarding the role of breast milk-derived antibodies in modulating vaccine-induced immunity. Nevertheless, the evidence suggests that although maternal antibodies may theoretically reduce vaccine immunogenicity, the overall protective benefits of breastfeeding outweigh any potential interference with vaccine responses. Full article

(This article belongs to the Special Issue Maternal and Infant Vaccines)

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14 pages, 871 KB

Open AccessArticle

Measles Surveillance in Tuscany (Italy), 2019–2024: A Six-Year Epidemiological Analysis

by Manuela Chiavarini, Rossella Romano, Andrea Guida, Elena Morelli, Camillo Di Nizio, Teresa Vladina Picchi, Giulia Napoli, Roberta Murolo, Vittorio Filieri, Barbara Rita Porchia, Daniela Senatore, Giovanna Bianco, Paolo Bonanni, Sara Boccalini and Angela Bechini

Vaccines 2026, 14(7), 558; https://doi.org/10.3390/vaccines14070558 - 25 Jun 2026

Abstract

Background: Despite sustained public-health efforts, measles continues to re-emerge in Europe. According to the ECDC, 1045 measles cases were reported in Italy in 2024. We describe epidemiological trends and characteristics of measles cases in the Tuscany Region from 2019 to 2024. Methods: We [...] Read more.

Background: Despite sustained public-health efforts, measles continues to re-emerge in Europe. According to the ECDC, 1045 measles cases were reported in Italy in 2024. We describe epidemiological trends and characteristics of measles cases in the Tuscany Region from 2019 to 2024. Methods: We conducted a population-based retrospective study using cases reported through the national surveillance system (PREMAL). Incidence rates were calculated using demographic data from the Italian National Institute of Statistics (ISTAT). Cases were stratified by year, sex, age group, vaccination status (2024), and hospital admission; temporal, demographic, and clinical trends were analysed. Results: From 2019 to 2024, 204 cases were reported, corresponding to a mean annual incidence of 0.93 per 100,000 population (95% CI: 0.80–1.07) and a cumulative incidence of 5.58 per 100,000 (95% CI: 4.78–6.31). Females accounted for 63.2% of cases (n = 129). After a peak in 2019 (n = 116), with an incidence of 3.13 per 100,000 (95% CI: 2.56–3.71), cases sharply declined during 2020–2023, followed by a resurgence in 2024 (n = 75), with an incidence of 2.05 per 100,000 (95% CI: 1.59–2.51). Children aged 0–4 years represented 7.4% of cases but had the highest age-specific incidence (12.19 per 100,000). Adults aged 25–64 years accounted for 70.1% of all cases, indicating the greatest absolute burden. Incidence was higher among individuals aged 25–44 years (11.56 per 100,000) than among those aged 45–64 years (4.30 per 100,000). Overall, 41.7% of cases required hospitalization. In 2024, most cases occurred in unvaccinated individuals (n = 56), while vaccination status was unknown for five cases. Conclusions: The 2024 measles resurgence in Tuscany mainly affected unvaccinated adults. These findings highlight persistent immunity gaps among adults, suggesting that protection and prevention measures are also needed in the population (0–4 y). Full article

(This article belongs to the Special Issue Communicable Diseases: New and Old Therapies and Preventive Strategies, 2nd Edition)

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15 pages, 2389 KB

Open AccessArticle

Immunogenicity of an Oil-in-Water Emulsion Containing Hafnia Alvei-Derived Lipopolysaccharide, with TLR4 and Dectin-2 Agonist Activity In Vitro

by Ri Ra Hong, Eun Ji Lee, Ji Hee Kwon, Sun Woo Im, Yeji Nam, Hyun-Tae Son, Eunhye Yoo and Hyung Tae Lee

Vaccines 2026, 14(7), 557; https://doi.org/10.3390/vaccines14070557 - 25 Jun 2026

Abstract

Background: Lipopolysaccharide (LPS) functions as a Toll-like receptor 4 (TLR4) agonist that triggers innate immunity; however, structural variations between pathogenic and commensal bacteria distinctly influence its immunostimulatory profile. This study evaluated the immunostimulatory activity of LPS derived from the commensal bacterium Hafnia alvei [...] Read more.

Background: Lipopolysaccharide (LPS) functions as a Toll-like receptor 4 (TLR4) agonist that triggers innate immunity; however, structural variations between pathogenic and commensal bacteria distinctly influence its immunostimulatory profile. This study evaluated the immunostimulatory activity of LPS derived from the commensal bacterium Hafnia alvei and explored its potential as an exploratory vaccine adjuvant. Methods: Cytokine induction was evaluated in immune cells across diverse host species, and receptor activation was assessed via reporter assays. To investigate in vivo immunogenicity and preliminary tolerability, H. alvei LPS was formulated into a prototype oil-in-water (O/W) emulsion utilizing ovalbumin (OVA) as a model antigen. Results: LPS from H. alvei strain BA2000346 exhibited immunostimulatory activity comparable to that of Escherichia coli, while inducing greater TNF-α expression than pathogenic Salmonella and Pseudomonas strains. Distinct from E. coli LPS, it demonstrated the capacity to activate both TLR4 and the mannose-recognizing Dectin-2 receptor in reporter systems. This cytokine induction was consistent across various strains and host species. Furthermore, the prototype O/W emulsion formulation enhanced antigen-specific humoral and cellular immune responses while demonstrating preliminary tolerability based on body-weight monitoring and visual clinical observation. Conclusions: H. alvei-derived LPS exhibits TLR4 and Dectin-2 agonist activity in vitro. When synergized with an O/W emulsion delivery system, it provides a preliminary indication of cross-species stimulatory potential and supports further investigation as a hypothesis-generating platform for future vaccine adjuvant development. Full article

(This article belongs to the Special Issue Advancements in Vaccine Research: Epidemiology, Immunogenicity, Effectiveness and Safety)

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