More than half a century after the initial discovery, hepatitis B virus (HBV) is one of the most common viral infections in humans. With a global heterogeneous prevalence, the HBV epidemic remains a monumental threat of health. In Asia, most HBV patients acquire the virus perinatally or in early childhood and develop a life-long chronic infection . The mechanisms of vertical HBV transmission include intrauterine infection and transmission during delivery . For example, the prevalence of chronic HBV infection in the general population ranged 11–20% in Taiwan during 1980s . Approximately, 40% of HBV carriers were born to HBsAg-positive mothers and 85–95% of newborns with HBV exposure consequently had chronic infection . Thus, mother-to-child transmission (MTCT) during the perinatal period is the major transmission route of HBV in hyperendemic areas . Prevention of MTCT is thus the most important strategy to reduce the global burden of HBV infection.