Objective:To explore the status of HBV infection, immune response to hepatitis B vaccine and its influencing factors of one-year old children born to HBV infected mothers in real world.Methods:In this cross-sectional study, eligible mothers infected with chronic HBV and children who completed standard vaccination against hepatitis B vaccine and hepatitis B immunoglobulin injection were selected. Clinical biochemical, virological measurements, data of antiviral therapy and complications during pregnancy and childbirth were collected by HIS(Hospital Information System)system and LIS (Laboratoty Information Management System) system. At one year of age, the children were tested for HBsAg, HBsAb and HBV DNA in venous blood specimens.Results:A total of 1 302 eligible mothers and children were collected, including 600 in high viral load group (mothers’ HBV DNA≥2×10 5 IU/ml) and 702 in low viral load group (mothers’ HBV DNA<2×10 5 IU/ml). In high viral load group, 587 patients received antiviral drugs in the middle or late trimester (Treated group) and 13 patients did not receive antiviral drugs (Untreated group). No chronic HBV infection occurred in children of low viral load group, and in 5 cases (0.83%) the infection occurred in high viral load group. In the five HBV infected children, 3 cases (0.51%) were in the treated group, and 2 cases (15.38%) in untreated group. The failure rate of mother-to-child blocking in low viral load group was significantly lower than that in high viral load group ( χ2=5.87, P=0.015), and it was significantly lower in treated group than that in untreated group ( χ2=29.195, P=0.001). The percentages of HBsAb level <10 mIU/ml, 10- <100 mIU/ml and ≥100 mIU/ml in 1 297 children without HBV infection were 1.15%, 15.65% and 83.19%, respectively. Univariate and multivariate logistic regression analysis showed that maternal total bilirubin level and hypothyroidism during pregnancy were correlated with HBsAb level at 1 year of age ( χ2=29.003, P <0.05). Conclusions:Antiviral drugs taken during pregnancy by pregnant women with high HBV viral load can significantly reduce mother-to-child transmission of HBV. Follow-up on the response of children born to HBV-infected mothers to hepatitis B vaccine should be enhanced after birth.