Vertical transmission of Hepatitis B virus HBV can result in a state of chronic HBV
infection and its complications. HBV vaccination with or without
hepatitis B immunoglobulin (
HBIG) prevents transmission of overt
infection to the babies. However, whether it also prevents occult HBV
infection in babies is not known. Consecutive pregnant women of any gestation found to be
HBsAg positive were followed till delivery, and their babies were included in the study. Immediately after delivery, babies were randomized to receive either
HBIG or placebo in addition to recombinant HBV
vaccine (at 0, 6, 10 and 14 weeks). The primary end-point of the study, assessed at 18 weeks of age, was remaining free of any HBV
infection (either overt or occult) plus the development of adequate immune response to
vaccine. The babies were further followed up for a median of 2 years of age to determine their eventual outcome. Risk factors for HBV transmission and for poor immune response in babies were studied. Of the 283 eligible babies, 259 were included in the trial and randomized to receive either
HBIG (n=128) or placebo (n=131) in addition to recombinant HBV
vaccine. Of the 222 of 259 (86%) babies who completed 18 weeks of follow-up, only 62/222 (28%) reached primary end-point. Of the remaining, 6/222 (3%) developed overt HBV
infection, 142/222 (64%) developed occult HBV
infection, and 12/222 (5%) had no HBV
infection but had poor immune response. All 6 overt
infections occurred in the placebo group (P=0.030), while occult HBV
infections were more common in the
HBIG group (76/106 [72%] vs. 66/116 [57%]; P=0.025). This may be due to the immune pressure of
HBIG. There was no significant difference between the two groups in frequency of babies developing poor immune response or those achieving primary end-point. The final outcome of these babies at 24 months of age was as follows: overt HBV
infection 4%, occult HBV
infection 42%, no HBV
infection but poor immune response 8% and no HBV
infection with good immune response 28%. Women who were anti-HBe positive were a low-risk group, and their babies were most likely to remain free of HBV
infection (occult or overt) and had good immune response to the
vaccine. Maternal
HBeAg-positive status and negativity for anti-HBe predicted not only overt but also any
infection (both overt and occult) in babies. In addition, high maternal HBV
DNA and treatment with
vaccine alone were significant factors for overt HBV
infection in babies. The current practice of administration of
vaccine with
HBIG at birth to babies born of
HBsAg-positive mothers is not effective in preventing occult HBV
infection in babies, which may be up to 40%. Because the most important risk factors for mother-to-baby transmission of HBV
infection are the replicative status and high HBV
DNA level in mothers; it will be worthwhile investigating the role of
antivirals and
HBIG administration during pregnancy to prevent mother-to-child transmission of HBV
infection.