ABSTRACT
The study compares the effect of two different doses of a recombinant DNA hepatitis B vaccine (Engerix-B) administered to 320 healthy adolescents divided randomly into two equal groups, using the 0, 1 and 6 month's vaccination schedule. Initially the larger dose elicited protective levels of antibody in a greater proportion of subjects. The seroprotection rates were significantly higher at both months 1 (17.6% v/s 9.2%) and 2 (68.8% v/s 56.7%). The difference was especially relevant 6 months after the start of the vaccination schedule when a 92.4% seroprotection rate was obtained in the 20 micrograms dose group, whereas only 78.3% of subjects in the 10 micrograms dose group had protective antibody levels. Furthermore there were significant differences in anti-HBs geometric mean titers for seroconverters at months 6 (109 v/s 56mlU/ml) and 7 (4774 v/s 2705mlU/ml). However one month after the third vaccine administration, both doses produced similar high seroprotection rates (97.9% and 97.1%, respectively). The difference in the generally mild overall reactogenicity for the 2 dose levels was not remarkable although the higher dose produced more local symptoms. The conclusion from the study was that the 10 micrograms dose produces a very good antibody response in adolescents, provided the full vaccination course of three doses, according to a 0, 1 and 6 month's schedule, is administered. However, the 20 micrograms dose should be used if compliance to the full course is in doubt since a 92.4% seroprotection rate can be obtained with 2 injections compared to only 78.3% with the 10 micrograms dose.