Safety, immunogenicity and antibody persistence of an inactivated hepatitis A vaccine in 4 to 15 year old children.

Among 277 healthy Venezuelan children, aged between 4 and 15 years, who were screened for hepatitis A virus (HAV) antibodies, 118 seronegative children were enrolled in an open study. Each child received one dose of the Pasteur Mérieux Connaught inactivated hepatitis A vaccine (AVAXIM¿trade mark omitted¿, 160 antigen units), followed by a booster dose 24 weeks later. All seronegative subjects seroconverted 2 weeks after immunisation (antibody titres greater, similar20 mIU/ml), and antibody titres were still over greater, similar20 mIU/ml after 24 weeks, at the moment of the booster dose. The anti-HAV antibody geometric mean titre (GMT), as measured by a modified radio-immunoassay (HAVAB(R), Abbott Laboratories, North Chicago, IL, USA), was 73.7 mIU/ml, 2 weeks after the first dose. Four weeks after the booster, the GMT value reached 6999 mIU/ml, representing a 29.6-fold rise from pre-booster levels. One year after the booster dose, the GMT value was 1673 mIU/ml in the 92 subjects who provided blood samples at this time, all of whom were still seroconverted ( greater, similar20 mIU/ml). No serious adverse event related to the vaccination occurred during the study. No immediate systemic reaction occurred. Local reactions were reported by 9.3% of subjects who received the primary injection and 5.5% of those given the booster dose. The systemic reactions were mainly fever and myalgia reported over the 7 days following the injection by 3.4% of subjects after the first dose and 5.5% of subjects after the booster dose. A clinically significant elevation of serum transaminase from pre-immunisation levels was noted in one subject (AST level 2.2 times the upper normal limit) 2 weeks after the first injection, although this was not associated with any clinical signs of impaired liver function. This trial demonstrated that AVAXIM¿trade mark omitted¿ containing 160 antigen units is safe and highly immunogenic in healthy children aged between 4 and 15 years, and could be included in the childhood vaccination schedule to control infection in areas endemic for hepatitis A.