A family cluster of an immune escape variant of hepatitis B virus infecting a mother and her two fully immunized children.

A hepatitis B virus (HBV) immune escape variant which results from a substitution of glycine by arginine at position 145 (arginine-145) in the immunodominant neutralization epitope of the S protein was found to infect one child in a seroepidemiologic survey of 1,812 vaccinated children. The child's mother and a younger brother were also infected by the same HBV variant, despite a greater than accepted level of protective antibody (anti-HBV surface antigen) in both the index child (30 mIU/ml) and the brother (> 20,000 mIU/ml). Our findings suggest the perinatal or horizontal transmission of the arginine-145 HBV variant from mother to child, but the ability of this variant to propagate among the vaccinated children remains unknown.