EARLY APPEARANCE OF NEUTRALIZING ANTIBODIES AFTER VACCINATION WITH ANINACTIVATED HEPATITIS-A VACCINE

Sera from 30 subjects vaccinated with the Pasteur Merieux Serums & Vac cins (PM) inactivated hepatitis A vaccine, and from 30 subjects vaccin ated with the Smithkline Beecham (SB) inactivated hepatitis A vaccine, were tested in two laboratories in order to provide comparative data on neutralizing activities of vaccine-induced antibodies, Sera were al so evaluated by a modified radioimmunoassay (mRIA) and results were co mpared to neutralization assays results. Neutralizing antibody titres provided by the two laboratories correlated well (coefficient or corre lation 0.42, P<0.001). Neutralizing antibodies were detected after vac cination with both vaccines, and the kinetics of neutralizing antibody were the same with both vaccines. The titres gradually increased betw een the second week after the first dose and the post-booster dose (we ek 28). A strong booster effect of the booster vaccine dose on neutral izing titres was observed. Significantly higher neutralizing antibody titres with the PM vaccine were observed as early immune respose on we ek 2 titres on both series of results. Vaccine-induced neutralizing an tibody titres and vaccine-induced antibody mRIA titres correlated well (coefficient of correlation 0.82 and 0.72, respectively, P<0.0001 in both cases). These results demonstrate early appearance of neutralizin g antibody at high titre with the PM vaccine.