FDA panel supports Moderna COVID-19 booster shots for older Americans, other adults at higher risk because of their health or profession The FDA committee voted 19-0 in favor of the recommendation. The Moderna booster shot will be a half-dose of the same vaccine already given. Data showed the lower dose was just as effective with potentially fewer side effects. The discussion of booster shots does not change the definition of "fully vaccinated," which remains two shots for the Pfizer-BioNTech and Moderna vaccines and one for J&J. Anyone required to be fully vaccinated for work or an activity will not need an extra shot.