Abstract: Persistent hepatitis B virus (HBV) infection can be classified into two categories:HBsAg-positive (overt HBV infection, overt-HBI) and HBsAg negative (occult hepatitis B infection, OBI).The understanding of overt-HBI is relatively clear; however, the knowledge of OBI remains limited.Mother-to-infant transmission is the main route of HBV transmission.Considering the existence of OBI, HBV transmission from mother to infant are composed of four types, (Ⅰ) overt-HBI to overt-HBI, (Ⅱ) overt-HBI to OBI, (Ⅲ) OBI to OBI, and (Ⅳ) OBI to overt-HBI.In the real world, current neonatal immunization strategy is based on mothers′ status of overt-HBI and has successfully blocked the type-Ⅰ transmission.However, the effects of HBV vaccine on the other three types are not clear.In this review, we focus on the threat and epidemic of OBI and describe the relationship between the four transmission types above and efficacy of HBV vaccination.We found that, in post-immunization era, the type Ⅱ may dominate mother-to-infant transmission of HBV.More studies on OBI should be conducted to reassess the effect of existing hepatitis B immunization strategies on HBV mother-to-child transmission.