Antibody and immune memory persistence after vaccination of preadolescents with low doses of recombinant hepatitis B vaccine.

Little is known about the impact of low-dose hepatitis B vaccine on the persistence of anti-HBs and immune memory in school-age children. Recombivax-HB 2.5 μg (RB) has been widely used in school-age children. RB induces high seroprotectionrates, but relatively low anti-HBs titers. The main objectives of this phase of the study were to assess anti-HBs persistence and the presence of immune memory 10 years post-vaccination of 8-10 year-old children with 3 doses of RB and the persistence of anti-HBs post-booster dose administration 5 (Group A; n=250) or 10 years (Group B; n=263) post-vaccination. No significant difference was observed between GMTs and the proportion of subjects with anti-HBs titers ≥ 10 mIU/mL 5 or 10 years post-vaccination. In both groups, a 56-fold decrease of anti-HBs GMTs was observed. One month post-booster, all but two subjects in Group A had an anti-HBs titer ≥ 10 mIU/mL. A 4.9- and 11.4-fold decrease in anti-HBs GMTs were observed during the first year post-booster in Group A and B, respectively. One year post-booster, the two groups were equivalent: ≥ 98.8% of subjects had an anti-HBs ≥ 10 mIU/mL. In group A, five years post-booster, 96.8% had a titer ≥ 10 mIU/mL; the GMT was 17-fold higher than the GMT 5 years post-vaccination (p<0.0001). In both groups, there was a strong positive correlation (p<0.0001) between anti-HBs titers observed post-primary vaccination and at following study time points (r=0.70-0.90). Three doses of RB administered at the age of 8-10 years induce a 10 years long-lasting immunity in virtually all vaccinees. The booster does not appear necessary on a 10 years perspective.