Viral hepatitis type B is a major health problem worldwide. Infection may progress to chronic liver disease, including cirrhosis and hepatocellular carcinoma. Age at acquisition of hepatitis B virus (HBV) infection is a key determinant of chronicity, since the rate of development of the hepatitis B surface antigen (HBsAg) carrier state is extremely high when infection occurs in newborns. This declines progressively with increasing age. Thus, universal vaccination of children during the first year of life is the most effective strategy to reduce the size of the carrier reservoir and to control the spread of HBV infection.

Hepatitis B vaccination is safe and effective, although breakthrough infections occasionally occur in vaccinees. In addition, HBV mutants with amino acid substitutions, within the common a determinant of HBsAg, have been identified, which can potentially escape vaccine-induced immunity. The most frequent HBV mutant, the so-called G145R, has a single amino acid substitution of glycine arginine at position 145 of the S gene.

Italy is one of the first countries to initiate a policy of universal and selective high-risk oriented vaccination against hepatitis B. Since 1983, babies born to HbsAg-carrier mothers have been given hepatitis B immune globulin (HBIG) and vaccine at birth. In 1991, vaccination became mandatory for all infants and 12-year-old adolescents. Screening of pregnant women for HBsAg in the last trimester of pregnancy, was recommended in Italy in 1983 and became mandatory in 1991. In 1998-1999, the researchers traced 522 children born to HBsAg- positive mothers who subsequently were immunized against hepatitis B in 3 public hospitals in the Campania region (southern Italy) during 1985-1994. For the present study, researchers obtained a blood sample from each child and mother. Information regarding the immunization schedule, type of vaccine administered (plasma derived or DNA recombinant), and hepatitis e antigen (HBeAg)/antibody (anti-HBe) status of the HbsAg-carrier mother at delivery was collected by use of a precoded questionnaire for each mother-child pair. In this study, 97 percent of children born to HBsAg carrier mothers who were immunized with HBIG plus vaccine at birth avoided HBV infection. Fourteen children (2.7 percent) seroconverted to anti-HBc without becoming carriers or developing disease, and none had detectable levels of HBV DNA. The data indicate that 5-14 years after immunization, 79.2 percent of children treated at birth with HBIG and vaccine still have anti-HBs antibodies at levels considered to be protective.

It is reasonable to speculate that the majority of children with undetectable antibodies may be protected against HBV, since the immunologic memory for HBsAg is thought to outlast the presence of circulating antibodies. Thus, routine administration of booster doses of vaccine to children may not be necessary, but additional information is needed to assess whether the immunologic memory in children vaccinated as infants persists into adolescence and adulthood, when the risk of infection, either by lifestyle or HBV professional exposure, becomes higher. In conclusion, the findings indicate that a hepatitis B vaccine administered at birth in association with HBIG provides immediate and long-term protection against HBV in children born to HbsAg- carrier mothers.

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