Single-dose hepatitis A vaccination: comparison of different dose levels in adolescents.

The effect of two dose levels of inactivated hepatitis A vaccine was investigated for immunogenicity and reactogenicity in an open study in adolescents. The subjects were randomized into two groups and to receive a priming dose of 720 EL. U or 1440 EL. U of hepatitis A antigen, respectively. A booster of the same dose level was given at month 6. In group 1, receiving 720 EL. U, the seroconversion rates at 15 days and 1 month were 92% and 99%. The corresponding rates for group 2, receiving 1440 EL. U, were 98% and 100%. Higher geometric mean titres of antibody to hepatitis A virus were noted at 1, 6 and 7 months in the group receiving 1440 EL. U. The vaccine was well tolerated in both groups. The most frequent side effect was transient soreness at the site of inoculation. No serious adverse reactions were observed. The study demonstrated that inactivated hepatitis A vaccine is safe and immunogenic at a dose level of 720 EL. U or 1440 EL. U in adolescents.