DELHI, India (Reuters Health) Oct 01 - Preterm infants from areas endemic for hepatitis B may need a four-dose schedule instead of the currently recommended three doses of hepatitis B vaccine, researchers from India report.

Dr. N. K. Arora and colleagues from the All India Institute of Medical Sciences in Delhi studied the response to hepatitis B vaccine in 60 term infants with intrauterine growth retardation and 82 premature infants. Infants born before 37 weeks of gestation were considered premature, while those born at term with weights below the 10th percentile were considered to have intrauterine growth retardation (term-IUGR).

Infants in both groups were administered four doses of a recombinant hepatitis B vaccine, with the first dose at birth and subsequently at 6, 10 and 14 weeks of age. Anti-hepatitis B immunoglobulin G (IgG) levels were measured before each dose of vaccine and then after the final dose. Antibody levels of at least mIU/mL were considered protective and a titer of at least 100mIU/ml was deemed a high response.

Dr. Arora and colleagues report in the September issue of Acta Paediatrica that the number of infants who achieved protective levels of antibodies after the third dose of vaccine was significantly greater in the term-IUGR group than in the premature group. This could be due to the immunological immaturity in the premature neonates, the investigators postulate.

The fourth dose of hepatitis B vaccine, however, produced a significant improvement in the antibody titers in the preterm infants and resulted in levels comparable to the term-IUGR group, the researchers report.

The presence of antibodies to hepatitis B in mothers, a common occurrence in endemic areas, also interfered with the immune response in preterm infants, the researchers note. This effect was not observed in term-IUGR infants, they add.

Gestational age is a better predictor of response to hepatitis B vaccination than birth weights, the researchers write. "Thus in the immunization schedule starting at birth, an additional dose of hepatitis B vaccine to preterm infants effectively overcomes immunologic handicaps," Dr. Arora and colleagues conclude.

Acta Paediatr 2002;91:995-1001.