Long-term protection against clinically significant breakthrough hepatitis B (HB) virus infection and chronic carriage depends on immunological memory, which allows a protective anamnestic antibody response to antigen challenge. Memory seems to last for at least 15 years in immunocompetent individuals. To date there are no data to support the need for booster doses of HB vaccine in immunocompetent individuals who have responded to a primary course. All adequately vaccinated individuals have shown evidence of immunity in the form of persisting anti-HBs and/or in vitro B-cell stimulation or an anamnestic response to a vaccine challenge. Nonetheless several countries and individuals currently have a policy of administering booster doses to certain risk groups. Boosters may be used to provide reassurance of protective immunity against benign breakthrough infection. For immunocompromised patients, regular testing for anti-HBs, and a booster injection when the titre falls below 10 mIU/mL, is advised. Long-term monitoring should continue, to confirm the absence of clinically significant breakthrough episodes of hepatitis B and to find out if a carrier state develops after 15 years. Also, non-responders to a primary course should continue to be studied.