You only need to get one dose of the Johnson & Johnson (Janssen) vaccine to be fully vaccinated. While the Johnson & Johnson (Janssen) vaccine is a single-dose vaccine, you may be eligible to receive a booster dose. A “booster dose” is another dose of a vaccine that is given to someone who built enough protection after vaccination, but then that protection decreased over time (this is called waning immunity). You are eligible for a booster if you are 18 or older and at least 2 months have passed since your single-dose Johnson & Johnson vaccine. You may choose to receive a single dose of any available COVID-19 vaccine for your booster (Pfizer, Moderna, or Johnson & Johnson). You are still considered fully vaccinated two weeks after your shot even if you don’t receive a booster.