Hepatitis B Virus Immunization and Neonatal Acquisition of Persistent Infection in England and Wales

It is believed that between 2% and 5% of infants born to hepatitis B virus (HBV)-infected mothers at a high risk of perinatal transmission will become persistently infected despite immunization starting at birth. We investigated factors associated with breakthrough infections.Sixty-nine samples from HBV-infected infants born between 2003 and 2015 were tested for HBV serological and molecular markers. Sequencing and epitope phenotyping were used to investigate alterations in hepatitis B surface antigen (HBsAg) sequence and antigenicity in infants and in mothers known to have transmitted and not to have transmitted virus to their infants.Vaccine/hepatitis B immune globulin uptake was complete in the majority of HBV-infected infants. A minority (8 [12%]) had detectable plasma antibody to HBsAg at 12 months. Twenty-five of 68 (37%) infants harbored a virus with amino acid changes in the HBsAg "a" determinant, of which 13 displayed altered HBsAg antigenicity. Viral load was 30-fold higher in maternal samples from those who transmitted.Our data provide evidence to suggest that immune selection drives change at mother-infant transmission, resulting in the alteration of HBsAg antigenicity. These changes may play a role in immunization failure, but other factors including viral load may be more important. Continued monitoring of vaccine efficacy is essential.