Long-term persistence of anti-HBs after vaccination with a recombinant DNA yeast-derived hepatitis B vaccine: 8-year results.

The aim of this study was to evaluate the persistence of antibodies 7 years after hepatitis B booster administration in healthy adult volunteers who were vaccinated in 1986. In October 1986, 188 seronegative, healthy adult volunteers (117 men and 71 women) were vaccinated with a 20 micrograms dose recombinant DNA yeast-derived hepatitis B vaccine. Mean age of the study group was 23.3 years (+/- 0.28). Immunisation was carried out according to a 0-1-2 month vaccination schedule, with a booster dose at 12 months. Of the 159 subjects who received the full vaccination course, 63 (40%) had a blood sample taken 8 years after the first vaccination. Of these 63 subjects, five were excluded from the analysis due to an irregular vaccination schedule and four subjects did not complete the accompanying questionnaire on possible booster administration. So, 54 subjects remained available for further analysis. Fourteen individuals had received an additional booster of hepatitis B vaccine sometime between 1989 and 1994. The geometric mean titre (GMT) at month 13 for these 14 individuals was 1494 mIU ml-1, compared with 3103 mIU ml-1 for those who did not receive an interim booster. Forty subjects, who received no additional booster dose besides that of month 12, met the inclusion criteria of the follow-up study. Of these, all subjects except one were seropositive for anti-HBs at month 96 (GMT: 215.9 mIU ml-1). All subjects were still anti-HBc negative at that time. Distribution of individual antibody titres revealed that overall 92.5% of subjects retained protective antibody levels (> or = 10 mIU ml-1); 72.5% of vaccinees retained high levels of anti-HBs (> or = 100 mIU ml-1) as compared to 99.2 and 97.0% at month 13, respectively. A positive correlation was found between the subjects' titres at month 13 and month 96. A 0-1-2 dose vaccination course with a booster dose administered at month 12, induces a protective immune response which lasts at least until 7 years after the full vaccination course of the subjects. A positive correlation was found between the anti-HBs antibody titres at month 13 and month 96.