Evaluation of COVID-19 vaccine effectiveness: interim guidance, 17 March 2021

This document provides interim best practice guidance on how to assess COVID-19 vaccine effectiveness (VE) using observational study designs. It discusses critical considerations in the design, analysis and interpretation of COVID-19 VE evaluations, as biased results may be produced even in settings where data completeness and quality are high. This guidance is targeted mostly for evaluations undertaken in low- and middle-income countries (L/MICs), but most of the concepts apply to VE evaluations in high- income settings as well.