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 volun teers, all of whom were negative for antibody to HAV (anti-HAV), were divided into three dosage groups, 1.0, 0.5 and 0.25-mu-g of viral prot ein, respectively. Each group received a total course of three intramu scular injections at months 0, 1 and 6. Slight side effects were noted after 16 of 99 injections and the occurrence and degree were almost i dentical to those of other commercial vaccines. On the other hand, all subjects had measurable titres of serum anti-HAV neutralizing antibod ies 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 an d 0.25-mu-g 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 b ody weight of immune serum globulin (ISG).