Immune Correlates and Vaccine Immunobridging: Statistical Innovations, Challenges, and Opportunities

In immunobridging, an investigational vaccine is approved based on a randomized trial of this vaccine versus an approved vaccine with an immunogenicity primary endpoint. Justification for immunobridging requires demonstration that meeting trial success criteria implies the investigational vaccine provides worthwhile protection against a relevant endpoint for a context of use. We consider recent statistical approaches whose integration supports immunobridging: (1) variable importance prediction analysis characterizing immune markers as correlates of risk; (2) controlled risk causal analysis evaluating markers as correlates of protection; and (3) transportability analysis combining data from efficacy and immunobridging trials for estimating investigational versus approved relative-vaccine efficacy.