Studies show that COVID-19 vaccines are effective, especially at keeping adults and children from getting seriously ill even if they do get COVID-19. Learn more about the benefits of getting vaccinated.
COVID-19 vaccines teach our immune systems how to recognize and fight the virus that causes COVID-19. It typically takes 2 weeks after vaccination for the body to build protection (immunity) against the virus that causes COVID-19.
People are considered fully vaccinated 2 weeks after their second dose of the Pfizer-BioNTech or Moderna COVID-19 vaccines, or 2 weeks after the single-dose Johnson & Johnson’s Janssen COVID-19 vaccine. To receive the most protection, people should receive all recommended doses of a COVID-19 vaccine. Learn more about who is recommended to get an additional primary dose or a booster dose.
People can sometimes get COVID-19 after being fully vaccinated. However, this only happens in a small proportion of people, even with the Delta variant. When these infections occur among vaccinated people, they tend to be mild.
Learn more about the effectiveness of COVID-19 vaccines.