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

The high cost of hepatitis B vaccines remains an obstacle to their use. Since the recommended adult dose of Recombivax HB (MSD) is 10 μg and that of Engerix B (SKB) is 20 μg, we sought to determine if 10 μg doses of each vaccine are equally immunogenic. Further, since 5 μg doses of Recombivax are routinely used in those ≤ 29 years of age in the US military, we sought to compare this dose with 5 μg doses of Engerix B. Lower doses of Engerix would result in vaccine cost savings. Methods: members of the Belize Defence Force who were ≥ 18 years of age (median 24) without detectable anti-HBc were randomly assigned to receive Recombivax, 5 or 10 μg, or Engerix, 5 or 10 μg 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 μg ( n =22) or 5 μg ( n =46) with GMC anti-HBs of 744 and 570 mIU ml −1 , respectively. Similar propertions in the two groups developed ≥ 10 mIU ml −1 anti-HBs (100 and 98%). Among the 91 people who received Engerix 10 μg, the GMC anti-HBs was 325 mIU ml −1 and 91% developed ≥ 10 mIU ml −1 . The 87 people who received Engerix 5 μg had the lowest GMC, 177 mIU ml −1 ( p <0.05 compared with either Recombivax group). Only 86% attained ≥ 10 mIU ml −1 anti-HBs ( p >0.05 compared with other regimens). The proportion attaining ≥ 100 mIU ml −1 was lower in the 5 μg Engerix group (63%) compared with 80% in the 5 μg or 95% in the 10 μg Recombivax groups ( p <0.05). Conclusions: Engerix administered in 5 μg doses is less immunogenic than 5 or 10 μg doses of Recombivax. In healthy populations < 30 years of age, regimens of half the recommended adult dose (5 μg of Recombivax or 10 μg of Engerix) are highly immunogenic and may result in significant vaccine cost savings.