Important update: Healthcare facilities
CDC has updated select ways to operate healthcare systems effectively in response to COVID-19 vaccination. Learn more
UPDATE
Given new evidence on the B.1.617.2 (Delta) variant, CDC has updated the guidance for fully vaccinated people. CDC recommends universal indoor masking for all teachers, staff, students, and visitors to K-12 schools, regardless of vaccination status. Children should return to full-time in-person learning in the fall with layered prevention strategies in place.
UPDATE
The White House announced that vaccines will be required for international travelers coming into the United States, with an effective date of November 8, 2021. For purposes of entry into the United States, vaccines accepted will include FDA approved or authorized and WHO Emergency Use Listing vaccines. More information is available here.
UPDATE
Travel requirements to enter the United States are changing, starting November 8, 2021. More information is available here.

COVID-19 Vaccines are Effective

COVID-19 Vaccines are Effective
Updated Dec. 23, 2021
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An illustrated image of two parents and a young child, all wearing masks, with the father holding a shield showing the word “vaccine” on the front.
  • COVID-19 vaccines are safe and effective.
  • COVID-19 vaccination helps protect adults and children ages 5 years and older from getting sick or severely ill with COVID-19 and helps protect those around them.
  • Some people who are vaccinated against COVID-19 will still get sick and have a vaccine breakthrough infection because no vaccine is 100% effective.

COVID-19 Vaccines Work
How and Why CDC Monitors Vaccine Effectiveness

An illustrated image of two parents and a young child, all wearing masks, with the father holding a shield showing the word “vaccine” on the front.

Vaccine Effectiveness

Vaccine effectiveness is a measure of how well vaccination protects people against outcomes such as infection, symptomatic illness, hospitalization, and death. Vaccine effectiveness is typically measured through observational studies specifically designed to estimate individual protection from vaccination under “real-world” conditions.

Data on Vaccine Effectiveness and Vaccine Breakthrough Infections

As part of CDC’s ongoing efforts to understand how well COVID-19 vaccines are working, CDC is monitoring vaccine effectiveness and rates of breakthrough infections, hospitalizations, and deaths.

Centers for Disease Control and Prevention Morbidity and Mortality Week Report logo

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

About Vaccine Effectiveness

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For Healthcare Professionals and Health Departments