Booster response to recombinant yeast-derived hepatitis B vaccine in vaccinees whose anti-HBs responses were initially elicited by a plasma-derived vaccine.

One hundred and eight primary school students who had been vaccinated with three doses of a plasma-derived hepatitis B vaccine were randomly divided into two groups, to receive a booster dose of either the same vaccine or of a recombinant yeast-derived vaccine. The pre-booster anti-hepatitis B surface antigen (HBs) geometric mean titres (GMT) were similar in both groups (281.8 mIU ml-1 versus 295.1 mIU ml-1, p greater than 0.5). One month after booster vaccination, all the vaccinees in both groups had a marked elevation in their anti-HBs titres, the anti-HBs GMT in group 1 and group 2 being 19,952.6 and 51,286.1 mIU ml-1 (p less than 0.05), respectively. In conclusion, the recombinant yeast-derived hepatitis B vaccine was able to elicit an excellent booster response in vaccinees who had originally received a plasma-derived vaccine.