Are Some COVID-19 Vaccines Better Than Others? Interpreting and Comparing Estimates of Efficacy in Vaccine Trials

COVID-19 vaccine trials provide valuable insight into the safety and efficacy of vaccines. Simple comparison of trial efficacy estimates, however, is problematic. When comparing efficacy results from COVID-19 vaccine trials, factors related to trial context and design must be considered. Coronavirus disease 2019 (COVID-19) vaccine trials provide valuable insight into the safety and efficacy of vaccines, with individually randomized, placebo-controlled trials being the gold standard in trial design. However, a myriad of variables must be considered as clinical trial data are interpreted and used to guide policy decisions. These variables include factors such as the characteristics of the study population and circulating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) strains, the force of infection, the definition and ascertainment of endpoints, the timing of vaccine efficacy assessment, and the potential for performance bias. In this Viewpoints article, we discuss critical variables to consider when comparing efficacy measurements across current and future COVID-19 vaccine trials.

Automated summary

COVID-19 vaccine trials offer valuable insights into the safety and efficacy of vaccines, but comparing efficacy results is not straightforward. Factors related to trial context and design must be considered when making such comparisons.