Seroepidemiology of hepatitis B virus infection in children 12 years after China's expanded program on immunization in Qamdo, Tibet.

Although hepatitis B vaccine (HepB) was first recommended through China's Expanded Program on Immunization (EPI) in 1992, Tibet was able to offer universal HepB vaccination starting only in early 2004. This cross-sectional study was conducted to assess, 12 years after administration of HepB, the seroepidemiology of hepatitis B virus (HBV) infection in children in Qamdo, Tibet. Focusing on a population of individuals ≤ 15 years of age living in Tibet, we analyzed serum samples from 261 healthy children for HBV status based on the presence of hepatitis B surface antigen (HBsAg), antibodies against HBV core antigen (anti-HBc), and antibodies against HBsAg (anti-HBs). Of all participants, 87.4% had received HepB vaccination. The overall anti-HBs-positive rate was 30.7%, with isolated anti-HBs in 75 participants (28.7%). Of all those studied, 13 (5.0%) were positive for HBsAg and 18 (6.9%) for anti-HBc. Participants who received vaccination in hospital at delivery had a lower prevalence of HBsAg than that of those born at home. By reducing HBV transmission, the EPI in Tibet protected most Tibetans younger than 15 years from becoming HBV carriers.