COVID Update: Masks are still required in health care settings, even if you’re fully vaccinated. Read our FAQs.

Coronavirus (COVID-19)

Updated Sep. 24, 2021 — If you need a COVID-19 vaccine or qualify for an additional dose or booster per CDC guidelines, please get your vaccine wherever possible. Available options can be found at vaccines.gov.

The science behind COVID vaccines

The science behind COVID vaccines

  • mRNA vaccines — Vaccines from Moderna and Pfizer are mRNA vaccines, a new approach to vaccinations. Johnson & Johnson is a viral vector vaccine
  • Vaccine safety — COVID-19 vaccines are safe and effective. Millions of people in the United States have received COVID-19 vaccines under the most intense safety monitoring in U.S. history. 
  • Vaccine dosage — The Pfizer and Moderna vaccines are administered in two doses, with the second shot given three to four weeks respectively after the first. The Johnson & Johnson vaccine is a single dose.
  • What to expectSide effects include fever, body aches and fatigue. These minor reactions mean your immune system is working.
  • Vaccinations in the US — See how many total doses have been administered so far.

Frequently asked questions

Eligibility and scheduling questions

General vaccine questions

Specific medical questions