Beyond efficacy: the full public health impact of vaccines in addition to efficacy measures in trials

Vaccine efficacy reflects the proportionate reduction in disease incidence between unvaccinated and vaccinated individuals. While vaccines are typically licensed on the basis of demonstrated efficacy, the ultimate goal of vaccination is to achieve a significant public health impact in addition to the prevention of infection in an individual. In this respect, there is a need to provide a broader perspective that encompasses the capacity of a vaccination program to reduce microbial transmission; avert disease, disability and premature deaths; to lessen the pressure on health systems, and to reduce health inequities between populations. These issues are particularly relevant for some of the newer vaccines (e.g., rotavirus, dengue, and malaria vaccines) that demonstrate lower efficacy in high burden settings than traditional vaccines, but nevertheless could have a substantial overall public health impact in these settings.

Data on a vaccine’s public health benefits are often not available or may be incomplete. As a consequence, decision-makers and target populations may underestimate the justification for vaccine use, leading to delays in public immunization program introduction and to ongoing preventable disease burden. The slow introduction of a rotavirus vaccine in developing countries despite evidence of enormous decreases in severe disease and hospital utilization is one example.

In addition to helping inform decision-makers and target populations, measures beyond efficacy may have a role in vaccine licensure. Specifically, there is no a priori reason why regulatory agencies would notconsider the total disease burden preventable by vaccine as a complement to vaccine efficacy.