Comparison of the reactogenicity and immunogenicity of two different dose levels of hepatitis A vaccine in healthy children and adolescents

An open study was performed to compare the reactogenicity and immunogenicit y of an inactivated hepatitis A vaccine administered in two different doses and schedules to 460 healthy volunteers aged 3-18 years. Participants were randomized to two groups to receive either two doses of 720 ELISA Units (E L.U) inactivated hepatitis A per 0.5 ml dose according to a 0,6-month sched ule, or three doses of 360 EL.U according to a 0, 1, 6-month schedule. Tran sient local injection soreness was the most commonly reported symptom in al most half of both groups with no serious adverse events. One month after th e primary course (one dose of 720 EL.U and two doses of 360 EL.U), 99% of 7 20 EL.U vaccinees had seroconverted, compared with 100% seroconversion in t he 360 EL.U group. All vaccinees were seropositive after the booster dose o f both vaccines with geometric mean anti-HAV titers of 2,359 and 2,967 mIU/ ml in the 720 EL.U and 360 EL.U groups, respectively. The vaccine containin g 720 EL.U of antigen per dose offers the advantage of convenience and acce ptance of immunization afforded by a two-dose course of vaccination accompa nied by a comparable antibody response with that achieved after three doses of vaccine containing 360 EL.U of antigen per dose.