INACTIVATED HEPATITIS-A VACCINE - REACTOGENICITY, IMMUNOGENICITY, ANDLONG-TERM ANTIBODY PERSISTENCE

This trial evaluated the reactogenicity, kinetics of antibody inductio n, and long-term immunogenicity of a 720 enzyme-linked immunosorbent a ssay units (EL.U.) antigen dose of an inactivated hepatitis A vaccine (Havrix(TM), SmithKline Beecham Biologicals, Rixensart, Belgium). One hundred six healthy adult volunteers were enrolled to receive vaccine intramuscularly according to a 0, 1, and 6-month schedule. The vaccine was well tolerated. The most frequently reported local symptom was so reness, observed following 37.1% of all doses. Headache was the most f requently reported general symptom observed following 12.9% of documen ted vaccine doses. The administration of one vaccine dose induced sero positivity (anti-hepatitis A virus [HAV] greater than or equal to 20 m IU/ml) in 91% of all vaccinees 1 month later. The second vaccine dose resulted in seropositivity of the remaining vaccinees at month 2. All subjects remained seropositive for HAV antibodies at month 6, at which time the booster vaccine dose was given. At month 7, all vaccinees ha d anti-HAV titres > 200 mIU/ml. Serological results obtained at months 12, 18, 24, and 36 showed that antibodies against HAV induced by the vaccine booster dose persist for at least 30 months following its admi nistration. All 49 subjects followed up until month 36 had antibody ti tres greater than or equal to 20 mIU/ml. The geometric mean titre (GMT ) decreased by 60% from month 7 to month 12; between month 12 and 36, the GMT decreased by approximately 14% per period of 12 months. Accord ing to the vaccine-induced antibody kinetics and the magnitude of anti body level decrease over time, the predicted duration of antibody pers istence is estimated to be at least 20 years. (C) 1994 Wiley-Liss, Inc .