evaluation of serum anti-hbs concentration in children vaccinated with recombinant hepatitis b vaccine at birth

introduction: vaccination with the major surface antigen of hepatitis b virus (hbsag) induces anti-hbs antibody production and level of 10 iu/l is considered protective. it has been shown that the level of anti-hbs antibody does wane after vaccination. the aim of this study was to evaluate the persistence of anti-hbs antibodies in healthy iranian children 10 years after primary vaccination. methods: blood samples were collected from 146 children, 10 years after completion of primary hepatitis b vaccination course at birth. the sera were tested for anti-hbs, antibody to hepatitis b core antigen (anti-hbc) and hbsag by use of elisa technique. results: at 10 years after primary vaccination, 70 (47.9%) children had protective levels of antibody (anti-hbs> 10 iu/l) with mean titer of 68.1 iu/ml. moreover, 45 (30.82%) children were negative for anti-hbs antibody. distribution of children according to anti-hbs concentration revealed that the proportion of subjects with antibody titer of 0-10 iu/l, 10-100 iu/l, 100-500 iu/l and 500-1000 iu/l was 52.1%, 24.6%, 20.5% and 2.7%, respectively. all children were negative for hbsag, although anti-hbc was positive in 11 (7.5%) children. there was no difference in the seroprotection rates of males and females. conclusion: the results of present study show that after 10 years after primary vaccination with recombinant hb vaccine, 47.9% of the children had protective levels of anti-hbs antibody. on basis of the hbsag and anti-hbc results, it seems that effective immunological memory exists in children. additional follow-up studies need to be conducted to determine the duration of protection.