While mixing doses during a primary series is not recommended at this time, you may choose to receive a different vaccine for your booster shot if you have completed a primary series and are eligible for a booster. 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. Some people may have a preference for the vaccine type that they originally received, and others may prefer to get a different booster. CDC’s recommendations allow for this type of mix and match dosing for booster shots.