Abstract
Humoral immune responses are protective against hepatitis B virus (HBV) infection. We characterized B-cell phenotypic changes in infants of hepatitis B surface antigen positive mothers compared with normal and hepatitis B surface antigen negative infants at birth and 1 year after HBV immunization. Hepatitis B surface antigen positive infants had higher immature transitional B cells at birth, which normalized a year after immunization. Immature B-cell response to neonatal HBV exposure is associated with maternal-child transmission of HBV.