RANDOMIZED COMPARISON OF 5 AND 10 MU-G DOSES OF 2 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 mu g a nd that of Engerix B (SKB) is 20 mu g, we sought to determine if 10 mu g doses of each vaccine are equally immunogenic. Further, since 5 mu g doses of Recombivax are routinely used in those less than or equal t o 29 years of age in the US military, we sought to compare this dose w ith 5 mu g doses of Engerix B. Lower doses of Engerix would result in vaccine cost savings. Methods. members of the Belize Defence Force who were greater than or equal to 18 years of age (median 24) without det ectable anti-HBc were randomly assigned to receive Recombivax, 5 or 10 mu g, or Engerix, 5 or 10 mu g IM at 0, 1, and 6 months. Randomizatio n was weighted toward Engerix. Results. after 3 doses, geometric mean concentrations (GMC) of anti-HBs were highest among those receiving Re combivax 10 mu g (n = 22) or 5 mu g (n = 46) with GMC anti-HBs of 744 and 570 mlU ml(-1) respectively. Similar proportions in the two groups developed greater than or equal to 10 mlU ml(-1) anti-HBs (100 and 98 %). Among the 91 people who received Engerix 10 mu g, the GMC anti-HBs was 325 mIU ml(-1) and 91% developed greater than or equal to 10 mlU ml(-1). The 87 people who received Engerix 5 mu g had the lowest GMC, 177 mIU ml(-1) (p < 0.05 compared with either Recombivax group). Only 86% attained greater than or equal to 10 mlU ml(-1) anti-HBs (p > 0.05 compared with other regimens). The proportion attaining greater than or equal to 100 mlU ml(-1) was lower in the 5 mu g Engerix group (63%) compared with 80% in the 5 mu g or 95% in the 10 mu g Recombivax grou ps (p < 0.05). Conclusions: Engerix administered in 5 mu g doses is le ss immunogenic than 5 or 10 mu g doses of Recombivax. In healthy popul ations < 30 years of age, regimens of half the recommended adult dose (5 mu g of Recombivax or 10 mu g of Engerix) are highly immunogenic an d may result in significant vaccine cost savings.