Category: Vaccine Impact

Once a vaccine is licensed and introduced in the population, post-licensure studies are required to measure vaccine effectiveness and impact of vaccination programs on the population at large. We review from the public health evaluation perspective the effects of vaccine-related exposures, describe the methods used to measure them and their assumptions. We distinguish effects due to exposure to individual vaccination from those due to exposure to a vaccination program, as the latter depends on vaccine coverage, other population factors and includes indirect effects as well. Vaccine (direct) effectiveness is estimated by comparing vaccinated and unvaccinated individuals exposed to the same vaccination program.