Recombinant yeast hepatitis B vaccine compared with plasma-derived vaccine: immunogenicity and effect of a booster dose.

The immunogenic effect of recombinant yeast and plasma-derived hepatitis B vaccines administered at 0, 1 and 6 months was evaluated in 334 seronegative health professionals. The seroconversion rates following 10 micrograms, 5 micrograms and 2.5 micrograms doses of recombinant vaccine were similar to those observed after 20 micrograms doses of plasma-derived vaccine. The geometric mean antibody titres (G.M.T.) induced by 10 micrograms and 5 micrograms doses of recombinant vaccine were similar to those observed after 20 micrograms doses of plasma-derived vaccine. The G.M.T. values were lowest after 2.5 micrograms doses of recombinant vaccine. However, the recipients of the 2.5 micrograms had a significant anti-HBs response after a fourth (booster) dose of recombinant vaccine was given at 12 months. A booster dose of recombinant hepatitis B vaccine was given to 31 health professionals who had been successfully immunised with plasma-derived vaccine 5-7 years previously. A significant anamnestic response was observed in 30 (97%) of these individuals in spite of the fact that 16 (52%) had low or undetectable levels of anti-HBs before the booster dose was given.