Independent emergence of a vaccine-induced escape mutant of hepatitis B virus.

We investigated the case of a child who was vaccinated at birth against hepatitis B and was also given hepatitis B immune globulin, but who nevertheless later became infected with the virus. Hepatitis B virus-specific deoxyribonucleic acid covering the region of the genome encoding the predominant a epitope of hepatitis B surface antigen was amplified using the polymerase chain reaction and the nucleotide sequence determined. We present evidence for the independent emergence of an escape mutant, similar to that previously identified in Italy, where a substitution of arginine for glycine has occurred in the second loop of the a epitope.