How CDC Monitors Vaccine Effectiveness
To understand how well COVID-19 vaccines are working in real-world conditions over time, CDC uses a multi-layered approach, which includes ongoing analyses of surveillance data and studies of vaccine effectiveness.
Surveillance data allow us to monitor rates of COVID-19 cases, hospitalizations, and deaths by vaccination status.
Analyses of surveillance data can provide signals of potential changes in vaccine effectiveness.
These signals can then be further studied through more robust, controlled vaccine effectiveness studies conducted by CDC and partners.
The vaccine effectiveness studies help us better understand how well COVID-19 vaccines are working in different groups of people, against different health outcomes, and against different variants. Vaccine effectiveness is a measure of how well vaccination protects people against infection, symptomatic illness, hospitalization, and death.
Learn about how CDC monitors COVID-19 cases, hospitalizations, and deaths by vaccination status
Learn about how CDC studies COVID-19 vaccine effectiveness