A person is considered fully vaccinated if they have received one dose of the Johnson & Johnson vaccine. Those who received the Johnson & Johnson vaccine should get a booster if at least 2 months have passed since their single-dose primary regimen, and they are 18 years of age or older. The CDC has approved “mix and match” booster doses for those who are eligible for a booster dose after their primary series. 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. 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.