Important update: Healthcare facilities
CDC has updated select ways to operate healthcare systems effectively in response to COVID-19 vaccination. Learn more
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.
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.
Travel requirements to enter the United States are changing, starting November 8, 2021. More information is available here.

Reinfections and COVID-19

Reinfections and COVID-19
Updated Jan. 20, 2022

Reinfection with the virus that causes COVID-19 means a person was infected, recovered, and then later became infected again. After recovering from COVID-19, most individuals will have some protection from repeat infections. However, reinfections do occur after COVID-19. We are still learning more about these reinfections. Ongoing studies of COVID-19 are helping us understand:

  • How often reinfections occur
  • Who is at higher risk of reinfection
  • How soon reinfections take place after a previous infection
  • The severity (how serious the infection is) of reinfections compared with initial (the first) infections
  • The risk of transmission to others after reinfection
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About Variants

Viruses are constantly changing, including the virus that causes COVID-19. These changes can lead to the emergence of variants (new strains of the virus) that can increase the risk of reinfection. COVID-19 vaccines continue to be highly effective in protecting against severe illness. Vaccines are recommended for all people 5 years or older, including people who have been infected before.

What CDC is doing

CDC continues to work to better understand reinfections with COVID-19 to inform public health action. CDC is using a range of data sources to assess how often reinfections occur, who is most at risk for reinfection, and the risk of reinfection when there is community spread of Omicron or other virus variants. CDC has worked closely with public health jurisdictions and the Council of State and Territorial Epidemiologistsexternal icon (CSTE) to help states to count repeat infections in the same individuals over time.

An updated national surveillance case definition of COVID-19 was introduced on September 1, 2021, and includes criteria for counting new infections (reinfections) after previous probable or confirmed infections. CDC is working with multiple public health jurisdictions that are identifying reinfections to collect and analyze the data. CDC is publishing several analyses that use datasets from various sources, including cohort studies (which follow the same people over time):

How to Protect Yourself and Others