Clinical trial of a lyophilized inactivated hepatitis A candidate vaccine in healthy adult volunteers

The safety and immunogenicity of a lyophilized inactivated hepatitis A vaccine was tested in healthy adult male volunteers. Thirty-six volunteers, all of whom were negative for antibody to HAV (anti-HAV), were divided into three dosage groups, 1.0, 0.5 and 0.25 μg of viral protein, respectively. Each group received a total course of three intramuscular injections at months 0, 1 and 6. Slight side effects were noted after 16 of 99 injections and the occurrence and degree were almost identical to those of other commercial vaccines. On the other hand, all subjects had measurable titres of serum anti-HAV neutralizing antibodies as early as 2 months after the first injection. The mean values of serum anti-HAV neutralizing antibodies at 7 months in the 1.0, 0.5 and 0.25 μg dose groups were 64-, 12-, and 9-fold higher, respectively, than those observed at 5 days in five recipients given 7.5 mg kg −1 body weight of immune serum globulin (ISG).