A two-dose hepatitis B vaccine regimen: Proof of priming and memory responses in young adults

This study shows that two doses of a recombinant hepatitis B vaccine (10 μg or 20 μg of HBsAg per dose), administered 6 months apart to young, healthy adults, can induce an antibody (anti-HBs) response similar to that expected with the standard three-dose regimen of this vaccine given at intervals of 0, 1, and 6 months. While only 46-67% of the vaccinees displayed a protective anti-HBs titer of ≤10 mIU ml^-1 prior to the receipt of the second dose at 6 months, virtually all were primed as 97-99% of the subjects developed such a titer when tested a month after the second dose. Among vaccinees given 10 or 20 μg doses, respectively, the secondary rise in antibody following the second dose yielded geometric mean titers (GMTs) of 1103 and 2538 mIU ml^-1, respectively. The study further demonstrated that a two-dose regimen of vaccination induced strong immunologic memory for HBsAg, as a booster dose of vaccine given 2 years later resulted in a rapid and vigorous anamnestic antibody response.