COVID-19 Vaccine Effectiveness Research

This page provides information for public health professionals and researchers. For information for the general public, please see Monitoring Vaccine Effectiveness

Clinical trials are conducted to determine vaccine efficacy before the U.S Food and Drug Administration (FDA) determines whether to approve a vaccine. CDC and other partners assess COVID-19 vaccine effectiveness under real-world conditions after the FDA approves a vaccine. This helps us understand if vaccines are performing as expected outside the more controlled setting of a clinical trial, which tests a vaccine before approval.

Below you’ll find descriptions of current and planned vaccine effectiveness evaluations CDC is conducting with partners. The descriptions include the evaluation’s data collection platform, protocol (if available), outcome, population, and participating sites. Links to protocols that detail the evaluation designs are included when possible.

The list of evaluations is organized by type of study. Choose a category below to see a description of those evaluation.

Vaccine Effectiveness Evaluations by Design

Select a study design below to get more information about the evaluation’s name, population, outcome, protocol and participating sites:

Read all MMWR COVID-19 vaccine effectiveness and safety reports.

For the latest CDC data on COVID-19 vaccine effectiveness: CDC COVID Data Tracker

For more information on COVID-19 vaccine effectiveness: COVID-19 Vaccines are Effective.

Page last reviewed: March 22, 2022