Frequently Asked Questions about COVID-19 Vaccination

COVID-19 Vaccine Primary Series

The number of vaccine doses you need depends on which vaccine you receive.

• Two doses of Pfizer-BioNTech vaccine should be given 3 weeks (21 days) apart.
• Two doses of Moderna vaccine should be given 4 weeks (28 days) apart.
• Only one dose of Johnson & Johnson's Janssen (J&J/Janssen) vaccine should be given.

If you receive a vaccine that requires two doses, you should get your second shot as close to the recommended interval as possible. You should not get the second dose earlier than the recommended interval.

COVID-19 vaccines are not interchangeable for your COVID-19 vaccine primary series.

If you received a Pfizer-BioNTech or Moderna COVID-19 vaccine for your first shot, you should get the same product for your second shot.

Additional Primary Dose If You Are Immunocompromised

If you received a Pfizer-BioNTech (ages 12 and older) or Moderna (ages 18 and older) mRNA COVID-19 vaccine primary series and have a moderately to severely compromised immune system, you should receive an additional primary dose of the same mRNA COVID-19 vaccine at least 28 days after the second dose.

Additional primary doses are not interchangeable. The vaccine used for the additional primary dose should be same as the vaccine used for the primary vaccine series. If the mRNA vaccine product given for the first two doses is not available or is unknown, either mRNA COVID-19 vaccine product may be administered.

Currently, CDC does not recommend an additional primary dose if you received a single-dose J&J/Janssen COVID-19 vaccine or in children less than 12 years old with moderate or severely compromised immune systems.

Booster Shot

Everyone 18 years and older who is fully vaccinated is eligible for a booster.

If you get a booster shot you have the option to either get the same COVID-19 vaccine product as your primary series, or you can get a different COVID-19 vaccine. You may have a preference for the vaccine type that you originally received, and you may prefer to get a different booster. CDC's recommendations now allow for this type of mix and match dosing for booster shots (Pfizer-BioNTech, Moderna, or J&J/Janssen). You may consider the benefits and risks of each product and discuss with your healthcare provider which COVID-19 vaccine product is the most appropriate booster for you.

Currently, a booster shot is not recommended for children less than 18 years old.

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