Different degree of antibody response to hepatitis B virus vaccine in breast- and formula-fed infants born to HBsAg-positive mothers.

Antibody response to hepatitis B virus vaccine was compared in 47 breast- and 112 formula-fed infants born to hepatitis B surface antigen-(HBsAg-) positive mothers. No difference was observed as to the percentage of infants who seroconverted. However, formula-fed infants developed transient but significantly higher anti-HBs antibody levels as compared to breast-fed infants. Suppressive factors in human milk or orally induced tolerance may explain this finding. The latter hypothesis may be supported by the presence of HBsAg in more than half of the milk samples we studied.