Neonatal hepatitis B infection: clinical and immunologic considerations.

A chronic infection develops in the vast majority of newborn infants infected with the hepatitis B virus, compared with fewer than 10% of infected adults. The reason is probably related to the immaturity of the newborn immune response to infection, resulting in failure to completely eradicate the virus from hepatocytes. Studies of the newborn immune system demonstrate a variety of defects that may predispose infants to chronic hepatitis B infection, including diminished cytokine production, decreased cytotoxic activity, and a generalized suppression of the immune response. In addition, there is evidence that exposure of the fetus to certain maternal hepatitis B antigens and antibodies may adversely modulate the newborn immune response. This article reviews the epidemiologic, virologic, and immunologic aspects of newborn hepatitis B infection, and discusses the reasoning behind the recent recommendations for universal hepatitis B vaccination of newborn infants.