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 booster. Children who have not been vaccinated should receive the same type of vaccine for their first two vaccines if they receive Moderna or their first three vaccines if they receive Pfizer.
Some people may have a preference for the vaccine type that they originally received, and others may prefer to get a different booster. The CDC has guidance for everyone 6 months and older based on age and medical condition.