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.