Dr. Ajit Sood, and associates from the Dayanand Medical College and Hospital of Ludhiana in northern India, evaluated seroconversion rates following hepatitis B vaccine in 60 neonates whose mothers were free of hepatitis B infection. The infants were divided into 3 groups of 20: term neonates weighing over 2.5 kg; preterm neonates weighing between 1.8 and 2.49 kg; and neonates weighing between 1.2 and 1.79 kg.

Recombinant hepatitis B vaccine was given to all the neonates at the currently recommended three-dose schedule. Antibody response was determined 4 weeks after the second and third doses using microparticle enzyme immunoassay. The findings are reported in the March/April issue of the Indian Journal of Gastroenterology.

Dr. Sood and colleagues observed that all neonates in the first group, 90% in the second group, and 45% in the third group were good responders (>100mIU/mL) after the third dose of the vaccine.

The researchers noted a significant positive correlation of 0.74 between gestational age and seroconversion to hepatitis B vaccine. All of the neonates born at term, compared with none of the neonates born at 28 to 30 weeks gestation, were good responders after the final dose of the vaccine.

"The response to hepatitis B vaccine is influenced by gestational age," Dr. Sood's group concludes.

Inadequate cell-mediated immune response and low immunoglobulin levels are probably responsible for the poor vaccination response in preterm neonates, Dr. Sood and colleagues hypothesize.

Preterm neonates should be given hepatitis B vaccine as soon as possible, the researchers recommend. However, there is a need to assess their antibody response and to give a booster dose if the titers are low, they conclude.

Indian J Gastroenterol 2002;21:52-54.