Getting Your COVID-19 Vaccine | CDC

When you need a second shot

If you are receiving an mRNA COVID-19 vaccine (Pfizer-BioNTech COVID-19 vaccine or Moderna COVID-19 vaccine) you will need 2 vaccinations to be fully protected. COVID-19 vaccines are not interchangeable. If you received a Pfizer BioNTech or Moderna COVID-19 vaccine, you should get the same product (or brand) for your second vaccination. You should also get your second vaccination if you have side effects after the first vaccination, unless a vaccination service provider or your doctor tells you not to have it.

If you receive the vector COVID-19 viral vaccine, Johnson & Johnsons Janssen (J & J / Janssen) COVID-19 vaccine, you only need 1 vaccination.

Learn more about how to get your second shot.

People with moderately to severely compromised immune systems should receive an additional dose of the mRNA COVID-19 vaccine after the first 2 doses.