Safety and immunogenicity of a new formulation of an inactivated hepatitisA vaccine

The safety and immunogenicity of a new formulation of the inactivated hepat itis A vaccine, Avaxim(TM), was evaluated in 189 children, aged 18 months t o 15 years in a monocentric, open trial. Two vaccinations were given six mo nths apart. Enrollment was balanced within three age groups: 18 months to 3 years, 4-8 years and 9-15 years. Antibody titers were measured blindly by an independent laboratory using a modified radioimmunoassay. Two weeks afte r the first dose, seroconversion was achieved by 94.6, 94.3 and 96.4% of in itially HAV-seronegative subjects (antibody titre <20 mIU/ml) in each age g roup (youngest to oldest, respectively), with corresponding geometric mean titre concentrations (GMC) of 72.2, 54.3 and 47.1 mIU/ml. Just before the b ooster dose, the seroconversion rate was 100% in all groups. and the corres ponding GMC values were 163, 169 and 111 mIU/ml. All groups included, a 22. 6-fold rise in GMC. From prebooster let els was observed four weeks after t he booster dose. An explanatory analysis suggested a tendency for higher an tibody levels in younger children at all vaccination time points. Local rea ctions were noted in 18.2% of the vaccinees after the first dose and in 8.5 % after the booster dose. The rates of systemic reactions were 23.8% after the first dose and 11.4% after the booster dose. Overall, this trial demons trated the good safety and immunogenicity profile of this vaccine in childr en aged 18 months to 15 years of age, (C) 1999 Elsevier Science Ltd. All ri ghts reserved.