In your primary vaccine series, you should get the same kind of vaccine for both doses to be fully protected. Experts aren’t sure if the vaccines will work as well if you get two different kinds of vaccines for your primary series. If a mixed primary series is inadvertently administered, the series is complete, and doses do not need to be repeated.

 In the following exceptional situations, a different, age-appropriate COVID-19 vaccine may be used to complete a primary series at least 28 days from the last COVID-19 vaccine dose:

• The same vaccine is not available.
• The first dose is unknown.

A person starts but is unable to complete a primary series with the same COVID-19 vaccine due to a contraindication.