Abstract
BACKGROUND: The duration of protection following primary series vaccination against hepatitis B is unknown in children and adolescents. It has been shown that the level of anti-hepatitis B surface antigen antibodies (anti HBs Ab) declines over years after vaccination. OBJECTIVES: The aim of this study was to estimate the long-term immunity against hepatitis B virus infection among children and adolescents who had received a complete hepatitis B vaccination series during infancy. PATIENTS AND METHODS: In a cross-sectional study, the - anti-HBsAb levels of 840 vaccinated children and adolescents were determined by enzyme-linked immunosorbent assay. RESULTS: Hepatitis B seroprotection rates (anti HBsAb ≥ 10 IU/L) among vaccinated children and adolescents aged 1 and 18 years were 90% and 48.9%, respectively. The declining trend of geometric mean titer of anti-HBsAb levels was observed as changed from 272.3 IU/L to 94.1 IU/L in 1 and 18-year-old population, respectively. A significant negative correlation was found between age and anti-HBsAb levels (r = - 0.220, P = 0.0001). CONCLUSIONS: The results showed a declining trend in anti-HBsAb titers over the time after vaccination against hepatitis B virus in our region. Further studies are warranted to establish the need for a booster dose in cases that are at risk of hepatitis B virus infection.