Comparison study of the immunogenicity and safety of 5- and 10-mu g dosages of a recombinant hepatitis B vaccine in healthy infants

Background. It has been suggested that lower dosages of hepatitis B vaccine may be adequate for vaccinating infants and would be less costly, Objectives. To compare the immunogenicity and safety of 5 and 10 mu g of Engerix-B(R) recombinant hepatitis B vaccine given to healthy infants, Methods. A prospective randomized comparison of 5- and 10-mu g doses of Engerix-B(R) recombinant hepatitis B vaccine given to infants at 2, 4 and 6 months of age. Seroconversion (antihepatitis B surface antigen (anti-HBs) greater than or equal to 1 mIU/ml) and seroprotection (anti-HBs greater than or equal to 10 mIU/ml) rates as well as geometric mean antibody titers were compared at 4, 6 and 8 months. Results. A total. of 190 healthy infants were screened and received the first dose of vaccine, Of these infants 153 were eligible to continue in the study. Both dosages proved to be highly immunogenic, producing high seroconversion and seroprotection rates and geometric mean anti-HBs concentrations after 3 doses. Although 10 mu g induced significantly greater geometric mean concentrations (1641 mIU/ml compared 880 mIU/ml at 8 months of age), the seroprotection rates were identical (98.5%). Conclusions, Both dosages were well-tolerated and no serious adverse experiences were reported, However, the 5 Erg of Engerix-B(R) administered at 2, 4 and 6 months of age did not induce as great an anti-Hbs concentration as did 10 mu g. Long term studies are required to determine whether using the lower dosage would sacrifice long term efficacy.