Understanding How COVID-19 Vaccines Work
This web page explains how the body fights infection and how COVID-19 vaccines protect people by producing immunity. It also describes the different types of COVID-19 vaccines that currently are available or are undergoing large-scale (Phase 3) clinical trials in the United States.
Understanding COVID-19 mRNA Vaccines
This fact sheet provides information about mRNA vaccines generally and about COVID-19 vaccines that use this new technology specifically.
Authorized and Recommended Vaccines
As COVID-19 vaccines are authorized and then recommended for use in the United States, it will be important to understand what is known about each vaccine. CDC will provide information on who is and is not recommended to receive each vaccine and what to expect after vaccination, as well as ingredients, safety, and effectiveness.
Currently, two vaccines are authorized and recommended to prevent COVID-19:
Vaccines in Phase 3 Clinical Trials
As of November 24, 2020, large-scale (Phase 3) clinical trials are in progress or being planned for two COVID-19 vaccines in the United States:
- AstraZeneca’s COVID-19 vaccine
- Janssen’s COVID-19 vaccine
Learn more about U.S. COVID-19 vaccine clinical trials, including vaccines in earlier stages of development, by visiting clinicaltrials.gov.