LONG-TERM IMMUNOGENICITY SAFETY AND EFFICACY OF A RECOMBINANT HEPATITIS-B VACCINE IN HEALTHY-ADULTS

Two hundred healthy adults seronegative for HBV markers received three 10 or 20 mcg injections of a vaccine formulated from HBsAg produced by a recombinant strain of the yeast Saccharomyces cerevisiae. The vaccine was administered intramuscularly at 0, 1, and 6 months in the deltoid region. The seroconversion rates, expressed in GMT/IU/l were determined at 1, 2, 6, 7, 12, 24, 36 and 48 months following the initial injection. No severe or serious adverse reactions attributable to the HB vaccines were observed in any subject. The seroconversion rates following the 20 mcg dose of recombinant vaccine were always higher than those observed after the 10 mcg dose, but the differences were not statistically significant. Also the GMT values were lower after the 10 mcg dose of vaccine. Females showed a higher anti-HBs response than males; an age-dependent effect was observed in the anti-HBs response as regards both the percentage of responders and the antibody concentrations in the serum. No adverse reactions to the vaccine were observed. The rDNA vaccine did not induce a response to yeast-derived impurities and did not increase anti-yeast IgE antibody titres. The results of this study have shown that the Amgen rDNA vaccine is safe and clinically well tolerated, and that it provides protection against infection and disease. A vaccination dose of 20 mcg appears more advantageous for healthy adult subjects.