Hepatitis A vaccination: schedule for accelerated immunization.

Hepatitis A vaccine, strain HM175, was investigated for immunogenicity and tolerability in a prospective multicentre trial. The following vaccination schedules and antigen contents were evaluated: days 0 and 14 with 720 ELISA units (El.U) of antigen, days 0 and 28 with 720 El.U and days 0 and 28 with 360 El.U. In all study groups, the seroconversion rates following two vaccinations were between 95 and 100%. Higher geometric mean concentrations of antibody to hepatitis A virus (anti-HAV) were reached by the vaccine containing 720 El.U of HAV antigen. The vaccine was equally well tolerated in all groups. In addition, an abbreviated schedule, in which 720 El.U of HAV antigen was given on days 0 and 14, resulted in 100% seroconversion by day 28 and a level of anti-HAV that was substantially higher than that observed after passive immunization. This implies that such a vaccine could replace immune globulin administration if time permits.