To be considered fully vaccinated, the Comirnaty (Pfizer) and Spikevax (Moderna) vaccine require two doses, and the Johnson & Johnson (Janssen) vaccine requires one dose. The Pfizer vaccine for children 6 months to 4 years old requires 3 doses. A booster dose is another dose of a vaccine that is given to someone who built enough protection after vaccination, but then that protection decreased overtime (this is called waning immunity).

Initial booster shots are recommended for those who are:

• Age 5 and older and completed their primary vaccination series of Pfizer at least 5 months ago
• Age 18 and older and completed their primary vaccination series of Moderna at least 5 months ago or completed their primary vaccination of Johnson & Johnson at least 2 months ago

If you are age 5 to 17, you must receive the Pfizer booster as it is the only booster approved for this age group. For primary and booster vaccination, people should receive an age-appropriate mRNA vaccine (Pfizer or Moderna). The Johnson & Johnson vaccine is authorized for anyone age 18 and older if no other approved vaccine is available. The CDC has approved mix and match booster doses. This means that a person can receive a booster of a COVID-19 vaccine that is different than the COVID-19 vaccine they received for their primary series or initial booster.

Second booster shots using an mRNA vaccine are recommended for those who are:

• Age 12 and older with weakened immune systems and received their initial booster at least 4 months ago
• Age 18 and older and received the Johnson & Johnson vaccine for their primary series and received a Johnson & Johnson booster dose at least 4 months ago
• Age 50 and older and received their initial booster dose at least 4 months ago

The CDC, in collaboration with the FDA and other public health partners, will continue to evaluate the need for additional booster doses for all individuals.