IMMUNOGENICITY OF HEPATITIS-B VACCINE IN TERM AND PRETERM INFANTS

Some studies have suggested that decreased seroconversion rates might be found in premature infants with low birthweight (< 2000 g) followin g administration of hepatitis B vaccine at birth. The aim of the prese nt investigation was to evaluate possible differences in seropositive rates between full-term and preterm infants after primary vaccination, in particular when gestational age of birthweight is very low. Two-th ousand and nine neonates born to HBsAg-negative mothers were vaccinate d with 10 mu g of recombinant hepatitis B virus (HBV) vaccine, from Ma y 1991 to October 1994. Children with infections, congenital malformat ions or serious illnesses were excluded. HBV vaccine was administered intramuscularly, on the fourth day of life and again at 1 and 6 months of age. A 1-ml blood sample was drawn from each infant 1 month after the third vaccine dose for determination of the level of anti-HBs anti body. The response to HBV vaccination was evaluated in 241 preterm (ge stational age <38 weeks) infants and 1727 term neonates. No statistica l difference was observed in the distribution of anti-HBs antibody lev el, either between preterm infants (<38 weeks) and newborns of normal gestational age, or between low birthweight (<2500 g) and normal weigh t infants. The results suggest that preterm and low birthweight infant s (<2500 g) respond to HBV vaccine in the same measure as normal-term infants.