RESUMO
Primary prevention by vaccination to increase herd immunity remains the main thrust in the control of hepatitis B virus [HBV] infection and many countries such as Islamic Republic of Iran have incorporated HBV vaccination into their national expanded program of immunization. This study was performed to determine the vaccine efficacy of hepatitis B infection between vaccinated and non-vaccinated school-aged children. Three hundred and ninety four students aged 6 to 8 years who received the hepatitis vaccine in the infancy and 314 students aged 9 to 10 years who did not receive it in Sepidan, southern Iran were enrolled. We also determined the titer of anti HBs Ab in the vaccinated students. Two students [0.5%] were HBV infected [positive HBC Ab] and none were a chronic carrier. Two hundred and forty nine students [63.2%] had anti HBs titer greater than 10 IU/ml. One hundred and seventeen students [30%] had anti HBs titer between 1 and 10 IU/ml and only 28 children had anti HBs titer less than 1 IU/ml. Five [1.6%] were HBV infected [positive HBc Ab] and 2 [0.6%] were chronic carriers [positive HBs Ag]. The efficacy of the vaccine 6-8 years after vaccination was 67.9% [95 Cl 78-92]. Our results showed that similar to other studies, vaccination could not reduce the infection rate but had a significant effect on the reduction of chronic infection and carrier state, emphasizing on the role of vaccination in the control of HBV infection in an endemic region