COVID-19 Vaccine Recommendations: Additional vs Booster Doses

There are two distinct uses for an additional dose of COVID-19 vaccine.

Additional dose after an initial primary vaccine series: administration of an additional vaccine dose when the initial immune response following a primary vaccine series is likely to be insufficient.

Booster dose: a dose of vaccine administered when the initial sufficient immune response to a primary vaccine series is likely to have waned over time. 

Currently, the CDC recommends certain groups should or may receive a booster shot of the Pfizer COVID-19 vaccine at least 6 months after full Pfizer vaccination. For more information, see the Pfizer-BioNTech COVID-19 Vaccine Booster Shot page on the CDC website. 

An additional dose is authorized by the FDA and recommended by the CDC.

COVID Vaccine Dosage Chart



Last updated October 5, 2021