Increased risk of developing chronic HBV infection in infants born to chronically HBV infected mothers as a result of delayed second dose of hepatitis B vaccination.

This two-stage study (cross-sectional and case-control) assessed the effects of delayed second dose HB vaccination on the risk of developing chronic HBV infection in infants born to chronically HBV infected mothers. 521 infants enrolled received the first vaccination by the end of the day after birth, without HBIG. 15 of these infants were chronically HBV infected. In the case-control comparison, controlling for HBeAg in the mother, the risk of an infant becoming chronically infected was 3.74 times (95% CI=0.97-14.39) higher if the interval between the first and the second doses exceeded 10 weeks. This finding suggests it is important that immunization programs ensure timely second dose vaccination to infants born to mothers with chronic HBV infection. Nevertheless, due to the small sample size, these findings should be verified by larger studies.