Background: In Iran scince 1992, hepatitis B vaccination was a part of the national vaccination program. Hepatitis B vaccination is effective in the epidemiology of hepatitis B. The aim ofthis study was to evaluate the long – term persistence of immunity.
Methods: This cross-sectional analytical study was conducted on children and adolescents aged between 6-18 years in Birjand, who received a three – dose hepatitis B vaccination in accordance with the national immunization program. No students were infected with hepatitis B. Antibody titer higher than10 IU/L was considered positive.
Results: A total of 530 patients (307 boys and 223 girls) were recruited for the study of which 44% had positive antibody titer (≥10 IU / L). The geometric concentration mean (GMCs) of antibody in subjects was 64.9±34.2, HBS antibody titer was positive in 40.4% of the boys and 59.6% of the girls. A significant difference in antibody titers was observed in terms of gender and according to the time elapsed since the last vaccination. Antibody titer in children older  than 13 years had passed since their last vaccination and was significantly less than those children younger than thirteen years old had passed since their vaccination logistic regression analysis showed that the only predictive factor of anti-HBS low titer (<10 IU/L) is elapsed time of vaccination.
Conclusions: Based on results of this study hepatitis B vaccine has created a good level of protection in 44% of the adolescents after 17 years