IMMUNOGENICITY AND SAFETY OF A NEW INACTIVATED HEPATITIS-A VACCINE INA COMPARATIVE-STUDY

A multicentre, controlled, randomised, open, comparative trial includi ng 839 healthy adult volunteers was carried out in order to compare th e immunogenicity and reactogenicity of two vaccines against hepatitis A virus (HAV) during primary immunization and after booster injection. The first vaccine was produced by Pasteur Merieux (PM), and the secon d vaccine by Smith-Kline Beecham (SKB). The vaccination schedule consi sted of 2 doses (months 0, 6) for PM and 3 doses (months 0, 1, and 6) for SKB. Two weeks after the first dose, the seroconversion rates amon g initially HAV seronegative subjects (n = 608) were 93.4% and 76.1% f or the PM and SKB vaccines, respectively, the corresponding geometric mean titres (GMTs) were 59.0 mlU/ml versus 30.8 mlU/ml (modified RIA H AVAB assay, Abbott Laboratories). Two months after the beginning of im munization (one dose versus two doses) the GMTs were 138.4 and 161.6 m lU/ml, respectively. At month 7, the seroconversion rates were 100% fo r both vaccines, and the GMTs were 4,189 and 3,163 mlU/ml, respectivel y. After the first dose of vaccine, 24.6% and 19.6% of the PM and SKB vaccinees reported local reactions. The rates for systemic reactions w ere 27.2% and 25.0%, respectively. Lower rates for local and systemic reactions were seen after booster injections and statistical differenc es were not observed between the two vaccines. The study also demonstr ated that vaccination was as well tolerated in subjects with anti-HAV antibodies as in HAV seronegative subjects. Logistic regression analys is revealed a significant vaccine effect on seroconversion rates only at week 2 (P < 10(-4)). The same conclusions were drawn from the analy sis of GMT by multivariate regression. When both times (week 2 and wee k 8) were analysed together, a statistically significant effect of int eraction between time and vaccine was observed, indicating that the ki netics of antibody responses were different. (C) 1995 Wiley-Liss, Inc.