Hepatitis B virus vaccination and antenatal transmission of HBV markers to neonates

The high prevalence of hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) in pregnant women is considered to be the most important factor contributing to the high carrier rate of HBsAg in some populations. Several factors, including the age at which infection occurs, predispose to the acquisition and frequency of the carrier state. The proportion of infected people who become chronic carriers ranges from about 80 to 95% for babies born to HBsAg/HBeAg-positive mothers. In this study of Indonesian infants receiving only active immunization against HBV, we measured the HBV markers passively acquired from their HBsAg-positive mothers. The relationship of these markers with vaccination response and with HBV infection status was studied longitudinally in the infants. In the exposed neonates from the HBsAg-positive mothers (n=61), the seroconversion rate to hepatitis B surface antibody (HBsAb) positivity was 95% after the first booster vaccination, with a geometric mean titre (GMT) of 2017 IUl-1. After 60 months, the GMT in this group decreased to 50 IUl-1. Four newborns in this group became HBsAg carriers. Of the four vaccination failures, three newborns were HBsAg/HBeAg positive at birth, suggesting that they had been infected in utero. No vaccination strategy (active alone, or passive/active) can prevent this transmission from occurring. One carrier was HBsAg negative at birth and up to month 4 but was HBsAg positive at month 12 and subsequently, suggesting a postnatal infection. Vaccination early in life can, to a large extent, prevent perinatal transmission and hepatitis B virus (HBV) infection later in infancy and childhood. In this study, the protective efficacy of the vaccination was 85% in the subcohort of neonates from HBeAg-positive mothers and 100% in the subcohort of neonates from HBeAg-negative mothers. Lack of maternal antibodies to hepatitis B core antigen (HBcAb) correlated strongly with transmission of HBV infection.