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Vaccines
Special Issues
Bacterial and Viral Infections: Current Challenges and Vaccine Innovations
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Bacterial and Viral Infections: Current Challenges and Vaccine Innovations

A special issue of Vaccines (ISSN 2076-393X). This special issue belongs to the section "Pathogens-Host Immune Boundaries".

Deadline for manuscript submissions: closed (30 November 2025) | Viewed by 10647

Editor

Dr. Dima El Safadi

E-Mail Website
Guest Editor
Liverpool School of Tropical Medicine, Department of Clinical Sciences, Liverpool L7 8XZ, UK
Interests: clinical trials; transmission of infectious diseases; one health approach
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Bacterial and viral infections remain significant global health challenges, with outbreaks and evolving pathogens continuing to strain healthcare systems worldwide. Vaccines have proven to be one of the most effective tools for preventing infectious diseases, yet gaps in vaccine access, development, and long-term efficacy persist. The dynamic nature of pathogens, the complexity of host immune responses, and logistical barriers in global immunisation efforts all contribute to these ongoing challenges.

This Special Issue brings together cutting-edge research and perspectives on the development, deployment, and impact of vaccines, with a focus on bacterial infections and their role in addressing antimicrobial resistance, as well as viral infections of global concern. It explores a wide range of topics, including the following:

  • Advances in vaccine platforms, including mRNA, viral vectors, and protein-based designs, for bacterial and viral targets.
  • The role of vaccines in addressing persistent and emerging infectious diseases, such as tuberculosis, pneumococcal infections, influenza, and COVID-19, with a focus on reducing antibiotic use and mitigating antimicrobial resistance.
  • Real-world effectiveness and implementation challenges, such as strategies to improve access, equity, and uptake.

By integrating scientific progress with practical implementation insights, this Special Issue aims to highlight the transformative potential of vaccines while addressing key challenges in their development and deployment. It provides a comprehensive resource for researchers, clinicians, and policymakers working to harness the power of vaccines in the fight against bacterial and viral infections.

Dr. Dima El Safadi
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-anonymized peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Vaccines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • bacterial and viral infections
  • vaccine platforms
  • antimicrobial resistance
  • vaccine effectiveness
  • vaccine access and equity
  • global health

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Published Papers (4 papers)

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Research

12 pages, 376 KB  
Article
Seroprevalence and Vaccination Determinants of Varicella Zoster Virus Among Pediatric and Adolescent Populations in Northern Lebanon
by Nourhan Farhat, Dima El Safadi, Jana Massoud and Sara Khalife
Vaccines 2025, 13(11), 1166; https://doi.org/10.3390/vaccines13111166 - 15 Nov 2025
Viewed by 1648
Abstract
Background: Varicella zoster virus (VZV) remains a significant cause of pediatric morbidity in populations in Lebanon, yet comprehensive data on population immunity and vaccination uptake are limited. This study aimed to estimate VZV seroprevalence and identify factors associated with immunity and vaccine uptake [...] Read more.
Background: Varicella zoster virus (VZV) remains a significant cause of pediatric morbidity in populations in Lebanon, yet comprehensive data on population immunity and vaccination uptake are limited. This study aimed to estimate VZV seroprevalence and identify factors associated with immunity and vaccine uptake among children and adolescents in Northern Lebanon. Methods: A cross-sectional study was conducted among 180 participants aged 1–18 years recruited from urban and rural settings in North Lebanon. After receiving informed parental consent, sociodemographic and clinical information were collected via structured questionnaires. Anti-VZV IgG and IgM antibodies were measured using validated Enzyme-Linked Immunosorbent Assays (ELISA). Associations with seropositivity and vaccination uptake were analyzed using multivariable logistic regression. Results: IgG seroprevalence was 79.4% (95% CI: 72.7–85.1), indicating prior exposure or immunization, while IgM antibodies, reflecting recent infection, were detected in 5.0% (95% CI: 2.3–9.4) of participants. Among vaccinated participants, IgG seropositivity was 63.6% (95% CI: 43.5–83.7) in the one-dose group and 89.5% (95% CI: 83.0–96.0) in the two-dose group. Completing the two-dose regimen was significantly associated with a higher IgG seropositivity (OR = 0.110, 95% CI: 3.2–52.4, p = 0.002). Parental reporting of history of varicella showed high sensitivity (99.0%) and overall accuracy (90.8%) in predicting seropositivity. Primary vaccination barriers included preference for natural infection (67%), perceived non-necessity (19%), and cost (10%). Regular pediatric follow-up strongly predicted vaccination (OR = 15.239, p < 0.001), whereas low parental awareness was associated with decreased vaccine uptake (OR = 0.027, p = 0.015). Conclusions: Suboptimal VZV vaccination coverage and persistent susceptibility underscore the need to integrate varicella vaccination into Lebanon’s national immunization schedule. Targeted educational efforts and enhanced pediatric healthcare engagement are critical to increasing vaccine uptake and reducing disease burden. Full article
(This article belongs to the Special Issue Bacterial and Viral Infections: Current Challenges and Vaccine Innovations)
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16 pages, 10159 KB  
Article
Design and Evaluation of a Broadly Multivalent Adhesins-Based Multi-Epitope Fusion Antigen Vaccine Against Enterotoxigenic Escherichia coli Infection
by Yanyan Jia, Ke Yang, Qijuan Sun, Weiqi Guo, Zhihao Yang, Zihan Duan, Shiqu Zhang, Rongxian Guo, Ke Ding, Chengshui Liao and Shaohui Wang
Vaccines 2025, 13(10), 1057; https://doi.org/10.3390/vaccines13101057 - 16 Oct 2025
Cited by 2 | Viewed by 3314
Abstract
Background: Enterotoxigenic Escherichia coli (ETEC) is a zoonotic pathogen causing diarrhea and mortality in infants and livestock. Its numerous serotypes necessitate the urgent development of multivalent vaccines for effective prevention, thereby reducing public health and economic threats. Methods: Computational bioinformatics analyses [...] Read more.
Background: Enterotoxigenic Escherichia coli (ETEC) is a zoonotic pathogen causing diarrhea and mortality in infants and livestock. Its numerous serotypes necessitate the urgent development of multivalent vaccines for effective prevention, thereby reducing public health and economic threats. Methods: Computational bioinformatics analyses were conducted on five major ETEC adhesins structural subunits (FaeG, FanC, FasA, FimF41a, and FedF). Dominant epitopes were selected and concatenated via flexible linkers, incorporating the PADRE sequence and LTb adjuvant to design a multi-epitope fusion antigen (MEFA). The recombinant MEFA protein was expressed in a prokaryotic system. Furthermore, molecular dynamics simulations, docking, and immune simulations assessed structural stability and immunogenicity. Immunoreactivity was tested by Western blot. Murine immunization evaluated antibody responses, lymphocyte proliferation, cytokine secretion, and protection against ETEC challenge. Results: Structural modeling showed an extended conformation, with docking and simulations indicating strong immune activation. Western blot confirmed MEFA immunoreactivity. MEFA induced high antigen-specific antibody titers, enhanced splenocyte proliferation, and increased IFN-γ and IL-4 secretion, indicating a Th2-biased response in mice. Vaccinated mice survived lethal ETEC challenge and maintained intestinal integrity. Conclusions: The MEFA candidate vaccine effectively induces robust humoral and cellular immune responses and provides protection against ETEC infection, representing a promising strategy for next-generation multivalent ETEC vaccines. Full article
(This article belongs to the Special Issue Bacterial and Viral Infections: Current Challenges and Vaccine Innovations)
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21 pages, 2518 KB  
Article
Preclinical Immunogenicity of a 6-Valent GBS Glycoconjugate Vaccine from a Repeat-Dose GLP Toxicology Study
by Aakriti Bajracharya, Gowri Chellappan, Florence Seal, Yutai Zhao, Giriraj Chalke, Neza Chowdhury, Harshita Seth, Jen Gan, Shangdong Guo, Kevin Pinder, Fong Chang, Drew Huff, Abby Mydland, Chloe Wright, Lais Conceicao, Winston Balasundaram, Rama Raghunandan, Anup Datta and Subhash V. Kapre
Vaccines 2025, 13(9), 952; https://doi.org/10.3390/vaccines13090952 - 5 Sep 2025
Cited by 3 | Viewed by 2583
Abstract
Background/Objectives: Group B Streptococcus (GBS) is a significant cause of perinatal infection in neonates and infants. Complications could include neonatal sepsis and meningitis, preterm birth, stillbirth, or death. Though no GBS vaccine is currently licensed, maternal immunization is expected to be a [...] Read more.
Background/Objectives: Group B Streptococcus (GBS) is a significant cause of perinatal infection in neonates and infants. Complications could include neonatal sepsis and meningitis, preterm birth, stillbirth, or death. Though no GBS vaccine is currently licensed, maternal immunization is expected to be a highly effective strategy to address invasive GBS disease—particularly in low- and middle-income countries (LMICs), where the disease burden is the greatest and access to existing interventions is limited. In this study, we present a novel hexavalent GBS vaccine candidate with a unique combination of serotypes (ST)—Ia, Ib, II, III, V, and VII—that could be an efficacious and cost-effective intervention, with the broadest coverage of 99% against circulating serotypes globally. Methods: The 6-valent conjugate vaccine candidate, GBS-06, is developed using a novel approach by linking the six polysaccharides (PS) to recombinant cross-reactive material 197 (rCRM197) carrier protein derivatized with a hydrazide-polyethylene glycol-hydrazide (HZ-PEG-HZ) linker. A repeat-dose GLP toxicology study with GBS-06 was conducted at the highest clinical dose of 20 µg in rabbits with saline as the placebo control. Results: The results reveal induction of robust anti-capsular polysaccharide-specific IgG responses against each of the six serotypes after each dose with the highest antibody GMCs at Day 49 following the third dose. Conclusions: Hence, this work is the first demonstration of strong immunogenicity achieved using a linker (HZ-PEG-HZ) for GBS glycoconjugate vaccine development. The positive data from the study have strong implications in the advancement of the candidate for evaluation in clinical trials and provide a licensure pathway for maternal immunization. Full article
(This article belongs to the Special Issue Bacterial and Viral Infections: Current Challenges and Vaccine Innovations)
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19 pages, 3631 KB  
Article
Biological Characterization and DIVA Potential of Three Rough Brucella melitensis Vaccine Strains
by Jinyue Liu, Yi Yin, Xinmei Yang, Mengsi Li, Jing Qu, Shaohui Wang, Yanqing Bao, Jingjing Qi, Tonglei Wu and Mingxing Tian
Vaccines 2025, 13(8), 857; https://doi.org/10.3390/vaccines13080857 - 13 Aug 2025
Cited by 3 | Viewed by 2153
Abstract
Background: Brucellosis is a zoonotic bacterial disease primarily controlled through quarantine, culling, and vaccination. Live attenuated vaccines remain the most effective countermeasure, yet their application is limited by residual virulence and diagnostic interference. This study developed three rough-type attenuated Brucella melitensis mutants (G7, [...] Read more.
Background: Brucellosis is a zoonotic bacterial disease primarily controlled through quarantine, culling, and vaccination. Live attenuated vaccines remain the most effective countermeasure, yet their application is limited by residual virulence and diagnostic interference. This study developed three rough-type attenuated Brucella melitensis mutants (G7, G8, G16) and evaluated their potential as DIVA (Differentiating Infected from Vaccinated Animals) vaccine candidates. Methods: Rough phenotypes were characterized through heat agglutination, acridine orange staining, and immunoblotting. Macrophage cytotoxicity was assessed via LDH release assays, while RT-qPCR analyzed macrophage activation capacity. Mouse infection and immunization-challenge experiments, complemented by histopathology, evaluated residual virulence and protective immunity. Antibody profiles were determined by ELISA, and DIVA capability was verified using LPS-coated ELISA. Results: G7 and G8 exhibited complete rough phenotypes, whereas G16 retained partial O-antigen (semi-rough). All rough mutants induced macrophage cytotoxicity and activation. The strains showed attenuated virulence with no viable bacteria recovered from spleens at 4 weeks post-inoculation. Histopathology revealed no liver lesions at 6 weeks post-inoculation. Immunized mice predominantly produced IgG2a-dominated Th1-type responses. The immune protection levels of G7 and G16 matched the reference vaccine M5–90Δ26, while G8 showed slightly lower efficacy. LPS-ELISA effectively differentiated vaccinated from infected animals via concurrent IgM/IgG detection. Conclusions: This study demonstrates that the rough-type B. melitensis mutants G7 and G16 serve as promising DIVA vaccine candidates, offering strong protection with low residual virulence while enabling serological differentiation between vaccinated and infected animals, highlighting their potential as effective vaccines for brucellosis control. Full article
(This article belongs to the Special Issue Bacterial and Viral Infections: Current Challenges and Vaccine Innovations)
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