Why are Some Immunized Children Still At Risk for HBV Infection?

Despite immunization, children born to mothers with replicating HBV (marked by hepatitis B e antigen, or HBeAg) are still at risk for infection, according to the April issue of Gastroenterology.

Mother-to-infant transmission is the major cause of hepatitis B virus (HBV) infection among immunized children. There have been proposals to screen pregnant women for HBeAg to determine if they carry a replicating virus, and give hepatitis B immunoglobulin (HBIG) to newborns, to prevent their infection.

To determine if these approaches are effective, Huey-Ling Chen et al. analyzed the rate of HBV infection among immunized children born to hepatitis B surface antigen (HBsAg)-positive mothers. HBIG was given to all the children with HBeAg-positive mothers (n=583) and to 723 of 1773 children with HBeAg-negative mothers. The children were given serology tests for HBV when they were 6 months to 10 years old.

Chen et al. found that HBeAg-positive mothers were more likely than HBeAg-negative mothers to pass the infection on to their children. A significantly greater percentage of children with HBeAg-positive mothers tested positive for antibodies against the hepatitis B core protein (16.76%) and HB surface antigen (HBsAg, 9.26%) than children with HBeAg-negative mothers (1.58% and 0.29%, respectively).  Among the HBV-infected children, the rate of chronic infection also was higher among children with HBeAg-positive mothers than  HBeAg-negative mothers (54% vs 17%).

The authors conclude that children born to HBeAg-positive mothers are at greatest risk for chronic HBV infection, despite immunization. Administration of HBIG to infants born to HBeAg-negative mothers didn’t appear to reduce the rate of chronic HBV infection, but might prevent infantile fulminant hepatitis.

The authors state that these findings justify population-based programs to identify HBeAg-positive pregnant women. The identification of HBV-infected children under the current immunization program indicates that new methods are needed to prevent transmission from these mothers, such as providing antiviral therapy in the third trimester to reduce the maternal viral load at the time of delivery.

According to the World Health Organization, in 2009, 177 countries had reported including the hepatitis B vaccine into their national infant immunization programs. Although universal infant immunization has significantly reduced the numbers of HBV carriers and rate of hepatocellular carcinoma, it currently cannot entirely eradicate mother–infant HBV transmission. Neonatal immunization can reduce the numbers of HBV carriers by only 75%–90%.

Chen et al. state that without screening programs for pregnant women, the childhood post-immunization surveillance program could not have been established and control of HBV in the second generation would be delayed.

New strategies to reduce the rate of breakthrough infection in children born to highly infectious mothers are being investigated and will be applied most readily in countries with adequate HBsAg and HBeAg screening of pregnant women.

More Information on Vaccination Against HBV

Read the article online.
Chen H-L, Lin L-H, Hu F-C, et al. Effects of maternal screening and universal immunization to prevent mother-to-infant transmission of HBV. Gastroenterology 2012;142:773-781.e2.

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