Randomized comparison of 5 and 10 microgram doses of two recombinant hepatitis B vaccines.

Unlabelled: The high cost of hepatitis B vaccines remains an obstacle to their use. Since the recommended adult dose of Recombivax HB (MSD) is 10 micrograms and that of Engerix B (SKB) is 20 micrograms, we sought to determine if 10 microgram doses of each vaccine are equally immunogenic. Further, since 5 microgram doses of Recombivax are routinely used in those < or = 29 years of age in the US military, we sought to compare this dose with 5 microgram doses of Engerix B. Lower doses of Engerix would result in vaccine cost savings.

Methods: members of the Belize Defence Force who were > or = 18 years of age (median 24) without detectable anti-HBc were randomly assigned to receive Recombivax, 5 or 10 micrograms, or ENgerix, 5 or 10 micrograms IM at 0, 1, and 6 months. Randomization was weighted toward Engerix.

Results: after 3 doses, geometric mean concentrations (GMC) of anti-HBs were highest among those receiving Recombivax 10 micrograms (n=22) or 5 micrograms (n=46) with GMC anti-HBs of 744 and 570 mIU ml-1, respectively. Similar proportions in the two groups developed > or = 10 mIU m-1 anti-HBs (100 and 98%). Among the 91 people who received Engerix 10 micrograms, the GMC anti-HBs was 325 mIU ml-1 and 91% developed > or = 10 mIU ml-1. The 87 people who received Engerix 5 micrograms had the lowest GMC, 177 mIU ml-1 (p < 0.05 compared with either Recombivax group). Only 86% attained > or = 10 mIU ml-1 anti-HBs (p > 0.05 compared with other regimens). The proportion attaining > or = 100 mIU ml-1 was lower in the 5 microgram Engerix group (63%) compared with 80% in the 5 microgram or 95% in the 10 microgram Recombivax groups (p < 0.05).

Conclusions: Engerix administered in 5 microgram doses is less immunogenic than 5 or 10 microgram doses of Recombivax. In healthy populations < 30 years of age, regimens of half the recommended adult dose (5 micrograms of Recombivax or 10 micrograms of Engerix) are highly immunogenic and may result in significant vaccine cost savings.