Why getting the second dose of your COVID-19 vaccine is so important

Like many other vaccines, the first two COVID-19 vaccines authorized by the Food and Drug Administration (FDA)—the Pfizer-BioNTech (Comiranty) and Moderna vaccine—require two doses. The vaccine will be given three or four weeks apart, depending on the vaccine being used.

The timing of your second dose of the COVID-19 vaccine will be coordinated by the organization that provided your first dose. The two-week window to receive your second dose begins 21 days after the first dose for Pfizer-BioNTech (Comiranty) and 28 days for Moderna.

Why are both doses needed?

Getting both doses of these vaccines maximizes your ability to receive full immunity from the vaccine. Receiving only one dose does not provide you with the full protection and does not give you the full effectiveness of the vaccine.

Will I be protected with just one dose?

For the two-dose vaccines, receiving one dose does provide you with some protection, though we do not know the full extent of the protection or how long it might last. Receiving only one dose is not as useful as receiving the full second dose. Given the spread of the virus and the serious health risk it poses, the second dose is strongly recommended.

If you’re contacted to schedule your second dose of a COVID-19 vaccine, please make every effort to receive it. It’s important to fully protect you and our communities.

Last reviewed: 
August 2021

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