Objective: To compare the immunogenicity and safety of 5 micrograms with 10 micrograms of Engerix-B recombinant hepatitis B vaccine when given to healthy children, 2 to 6 years of age.
Methods: Randomized multicenter study of serongative children 2 to 6 years of age who received Engerix-B hepatitis B vaccine either 5 micrograms/0.25 ml or 10 micrograms/0.5 ml (the current Food and Drug Administration-approved dosage of Engerix-B in children) at 0, 1 and 6 months. Serum was obtained at 1, 3, 6 and 8 months after the first vaccine dose was given for antibody measurement.
Results: A total of 223 subjects were screened and received the first dose of vaccine. Of these subjects 193 continued in the study. Both dosages proved to be highly immunogenic, producing high seroconversion and seroprotection rates and geometric mean antibody to hepatitis B surface antigen concentrations after 3 doses. The geometric mean concentrations of seroconverters at Months 6 and 8 were significantly greater for the 10-micrograms group compared with the 5-micrograms group. Both dosages were well-tolerated and no serious adverse events were reported.
Conclusions: There was a significant reduction in geometric mean concentrations on lowering the dosage of Engerix-B from 10 to 5 micrograms in children 2 to 6 years of age. Although a high seroprotection rate was elicited by the 5-micrograms dose, the lower antibody concentrations achieved may make this lower dosage less desirable in the long term. Further studies are required to examine the need for booster doses of vaccine with both dosing schedules.