GOOD IMMUNOGENICITY OF GBM STRAIN INACTIVATED HEPATITIS-A VACCINE IN HEALTHY MALE-ADULTS

A formalin-inactivated aluminium hydroxide adsorbed hepatitis A vaccin e was evaluated in a dose-response study on 195 healthy male adults (a ge range: 18-31 years) in two French hospitals (Lyon, Rouen). Four dos es (20, 40, 80, 160 RIA antigen units) were administered intramuscular ly (i.m.) in two injections over a 6-month period. At the time of the first vaccine injection, 32 subjects (16.4%) were found positive (>20 mIU ml(-1)) for HAV antibody (total Ig RIA HAVAB(R) assay, Abbott Labo ratories) and, were excluded from the analysis of immunogenicity crite ria. Fourteen days after the first vaccine injection, 78.1% (95% confi dence interval (CI): 62-90) of seronegative subjects who received the 160 RIA antigen unit dose seroconverted with a geometric mean titre (G MT) of 43 mIU ml(-1) (95% CI:33-56). Seroconversion was 100% (95% CI:9 1-100) at 1 month with a GMT of 95 mIU ml(-1) (95% CI: 79-112). Statis tical analysis revealed a significant dose-related effect (p < 0.0001) on GMT by multivariate regression analysis of the results after the f irst injection. Biological safety was evaluated and alanine aminotrans ferase and aspartate aminotransferase levels were similar prior to and 14 days after the first injection in the four groups. Reactions after injection were similar in the four dosage groups: 6.2% of subjects re ported immediate reactions after first vaccination (feeling sick, spon taneous pain, headache), 8.9% reported local reactions at the site of injection (spontaneous pain, haematoma, local adenopathy) and 13.5% re ported general reactions ('flu-like' syndrome, gastrointestinal tract disorders, fatigue, headache). After the booster, the incidences of re action were 1.6% for immediate reaction, 4.8% for local functions and 4.8% for general reactions. Based on these data the 160 RIA antigen un it dose will be used in the further clinical development of this vacci ne to confer rapid protection against HAV.