While COVID-19 vaccines are highly effective, no vaccine provides 100% immunity. Because this is a new virus, scientists and medical experts continue to monitor how long immunity lasts, whether some groups may need additional doses, and how well the vaccines protect against new variants of the virus.

Data continue to show that the COVID-19 vaccines are extremely effective in protecting fully vaccinated people from catching and spreading the virus, including the Delta variant, and scientists continue to monitor vaccine efficacy for new variants. A small percentage of vaccinated people experience breakthrough cases, but they are much more likely to have milder symptoms than unvaccinated people who get COVID-19.

Unvaccinated people continue to account for the vast majority of severe cases, hospitalizations, and deaths from COVID-19. CDC data show that in August 2021, the risk of dying from COVID-19 in the U.S. was more than 11 times greater for unvaccinated people than for fully vaccinated people.

The risk of severe illness from COVID-19 is elevated for some groups — including older adults, people with underlying medical conditions, immunocompromised people, and pregnant or recently pregnant women. If you have questions about your risk of COVID-19, how to protect yourself, or the vaccines, speak to your health care provider.

Updated December 9, 2021