# Designs for Vaccine Studies

## TL;DR

This paper discusses various study designs used to evaluate vaccines, including their direct and indirect effects on populations.

## Contribution

The paper highlights recent developments in vaccine study designs, such as target trial emulation and ring vaccination.

## Key findings

- Vaccination can have indirect effects on unvaccinated individuals.
- The ring vaccination trial design was first used during the Ebola outbreak.
- Methods for evaluating vaccine durability were developed for both blinded and unblinded studies.

## Abstract

Due to dependent happenings, vaccines can have different effects in populations. In addition to direct protective effects in the vaccinated, vaccination in a population can have indirect effects in the unvaccinated individuals. Vaccination can also reduce person-to-person transmission to vaccinated individuals or from vaccinated individuals compared with unvaccinated individuals. Design of vaccine studies has a history extending back over a century. Emerging infectious diseases, such as the SARS-CoV-2 pandemic and the Ebola outbreak in West Africa, have stimulated new interest in vaccine studies. We focus on some recent developments, such as target trial emulation, test-negative design, and regression discontinuity design. Methods for evaluating durability of vaccine effects were developed in the context of both blinded and unblinded placebo crossover studies. The case-ascertained design is used to assess the transmission effects of vaccines. The novel ring vaccination trial design was first used in the Ebola outbreak in West Africa.