COVID-19 Vaccine Efficacy and Effectiveness – the Elephant (Not) in the Room

Person Holding Laboratory Flask

Piero Olliaro, Els Torreele, Michel Vaillant Vaccine efficacy is generally reported as a relative risk reduction (RRR). It uses the relative risk (RR)—ie, the ratio of attack rates with and without a vaccine—which is expressed as 1–RR… Although the RRR considers only participants who could benefit from the vaccine, the absolute risk reduction (ARR), which […]