Systematic review protocol: evaluation of candidate platforms and vaccines for emerging and re-emerging viral threats

Emerging viral threats such as coronavirus, influenza, Lassa fever, Mpox, and Nipah virus continue to pose significant global health challenges. The development and deployment of effective vaccines are essential for outbreak control and pandemic preparedness. This protocol describes a systematic review that will synthesize evidence on vaccine candidates targeting high-priority viral threats and major vaccine platforms.

We will include randomised controlled trials (RCTs) assessing vaccine candidates for specified viruses (coronavirus, Lassa fever, Nipah virus, and Mpox) and platforms (protein-based, viral vector, and RNA) in the human populations. To encompass the full vaccine development landscape, exploratory and preclinical studies may also be included (any type of original research). Data sources will include MEDLINE Ovid, Embase Ovid (including ClinicalTrials.gov), and Cochrane Library (including CENTRAL), and grey literature (including conference proceedings, dissertations, trial registries, and company websites). Risk of bias will be assessed using Cochrane revised tool for assessing risk of bias in randomised trials (RoB-2) and Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE), and certainty of evidence will be evaluated using Grading of Recommendations Assessment, Development and Evaluation (GRADE). The primary outcomes are safety, immunogenicity, and vaccine efficacy or effectiveness, prioritised for their critical role in outbreak management and in guiding regulatory approval, public health policy, and clinical decision-making. Meta-analyses will be conducted where appropriate, using both fixed- and random-effects models. Subgroup analyses will be performed to explore heterogeneity based on virus type, vaccine platform, and outcome measures, where appropriate.

This review will provide a comprehensive synthesis of vaccine development efforts across multiple platforms and pathogens with epidemic or pandemic potential. It will inform future research, policy, and investment decisions in global health preparedness.

PROSPERO 2025 CRD420251082338 on 6 October 2025.