AbstractThe immunogenicity of a 5‐μg dose of vaccine (H‐B‐Vax, MSD) was evaluated in 50 young adults (17–19 years). Results were compared to our previous studies using similarly prepared vaccines using 20 μg and 10 μg per dose with the same trial protocol in a comparable population. Seroconversion rates for the 5‐μg doses of vaccine were 80% after the first dose and 98% after the second dose. The remaining participants did not develop anti‐HBs in the course of the trial. These results are not significantly different from those observed in the 10‐μg and 20‐μg studies. The increase of anti‐HBs titers was slower for the 5‐μg group. High geometric mean titers were observed after booster vaccination, but lower for the 5μg (3,591 mIU/ml) than for 10 μg (9,277 mIU/ml) and 20 μg (12,975mIU/ml) doses. It is concluded that 5‐μg dose of the vaccine is effectiv