Hepatitis B virus (HBV) infection is a worldwide health problem and mother-to-infant (or vertical) transmission is the main source of chronic infection in Asian countries. Administration of HBV vaccine to the infant at birth, with or without concurrent specific immunoglobulin, efficiently prevents such transmission (efficacy>90%). In France, testing Ag HBs is mandatory during pregnancy in all pregnant women. Infants born to Ag HBs-positive mothers should receive the first injection of vaccine and one injection of specific immunoglobulins at birth. Vaccination should thereafter be completed according to a three-injection protocol (at 1 and 6 months) or a four-injection protocol in case of prematurity. Failure of immunoprophylaxis can be observed when the viral load is very high in the mother during pregnancy (HBV-DNA levels>200,000 IU/mL). In such women, antiviral therapy with analogs (lamivudine, telbivudine, or tenofovir) during the third trimester of pregnancy and 1 month post-partum, in association with accurate immunoprophylaxis, may prevent vertical transmission. The optimal cut-off value of maternal viral load for antiviral therapy in late pregnancy and post-partum to prevent vertical transmission is still under debate.