IMMUNOGENICITY AND SAFETY IN ADULTS OF HEPATITIS-A VIRUS-VACCINE ADMINISTERED AS A SINGLE-DOSE WITH A BOOSTER 6 MONTHS LATER

An inactivated vaccine against hepatitis A was administered as a singl e 1,440 enzyme-linked immunosorbent assay (ELISA) units dose at month 0 with a booster at month 6 to 200 subjects divided into two age group s: group 1, 20-39 years (n = 134) and group 11, 40-62 years (n = 66). At day 15, the seropositivity rates were 90% and 77% in groups I and I I, respectively. At month 1 the seropositivity rate was 97% in both gr oups. At month 6 the seropositivity rates were 94% and 88% in groups I and II, respectively. One month after the booster, at month 7, 100% i n both groups had become seropositive. The vaccine was well tolerated and did not cause any severe reactions. The results indicate that a si ngle high vaccine dose offers protection against hepatitis A virus (HA V) for at least 6 months in the majority of cases where rapid vaccinat ion is required even in travellers of older age. A booster dose will e nsure long-term protection. (C) 1994 Wiley-Liss, Inc.