Reference:
Joi, P. (2020). What is the difference between efficacy and effectiveness? Gavi, the Vaccine Alliance. Retrieved from https://www.gavi.org/vaccineswork/what-difference-between-efficacy-and-effectiveness
Summary:
Efficacy and effectiveness are two crucial terms in vaccine science, often conflated but distinct. Efficacy refers to the performance of a vaccine under ideal, controlled conditions, typically demonstrated in clinical trials where a vaccinated group is compared to a placebo group. For instance, a vaccine may have an efficacy of 90%, indicating a significant reduction in disease cases compared to unvaccinated individuals. However, this does not guarantee the same level of effectiveness in the real world, where various factors, including population health, storage, and administration, can influence outcomes. Effectiveness is assessed through observational studies, comparing vaccinated individuals with those who are unvaccinated in the general population. Data collected from these studies is vital for understanding vaccine performance and ensuring public health strategies. Even vaccines with moderate effectiveness, like the influenza vaccine, can have a substantial impact on saving lives.