SAFETY AND IMMUNOGENICITY OF A LIVE ATTENUATED HEPATITIS-A VIRUS-VACCINE IN SERONEGATIVE VOLUNTEERS

Seronegative adults were enrolled in a dose-escalating study of a live attenuated hepatitis A virus (HAV) vaccine that was prepared from the F' variant of HAV strain CR326F. They were injected subcutaneously with 10(4.1), 10(5.2), 10(6.1), or 10(7.3) TCID50 of HAV vaccine (n = 40) or with placebo (n = 12) and were followed for 6 months. None of the vaccine recipients developed significant systemic reactions or aminotransferase elevations. HAV was not isolated in cell culture from any postvaccination serum or stool specimen tested. Antibody to HAV was detected by modifications of HAV antibody assays (HAVAB or HAVAB-M) in 20%, 40%, 60%, and 100% of the recipients of each vaccine dose, in ascending order. Neutralizing antibody was present in all 10(7.3) TCID50 recipients tested at 3 and 6 months after vaccination. This live attenuated HAV vaccine was well tolerated and highly immunogenic at a dose of 10(7.3) TCID50.