The design of emulated target trials and the application in evaluating vaccine effectiveness

Randomized controlled trials have long been regarded as the "gold standard" for evaluating vaccine efficacy. However, conducting RCTs for vaccines in real-world studies is not always feasible due to limitations in research resources and ethical considerations. In recent years, the emulated target trial, a novel research framework, has emerged. This method applies the design principles of randomized trials to observational studies by using observational data to emulate the randomization and grouping of a clinical trial, thereby assessing vaccine effectiveness in the real world. The application of emulated target trials enhances the quality and utility of real-world evidence. This article explains the fundamental principles, design elements, advantages, and limitations of using emulated target trials to evaluate vaccine effectiveness, providing theoretical methods and guidance for conducting such studies in China.