ABSTRACT
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. 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. 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. 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