AIM The study was conducted to evaluate the immunogenicity of an early, extra dose of enhanced inactivated poliovirus vaccine (IPV) administered simultaneously with recombinant hepatitis B vaccine (HBV) to preterm infants shortly after birth.

RESULTS At birth, a lower percentage of both study and control preterm infants had antipoliovirus type 3 titres ⩾ 1:8 than full term infants. At 1 and 3 months of age significantly more early IPV infants had antipoliovirus type 3 titres ⩾ 1:8 than routinely vaccinated preterm infants (p < 0.05). At 7 months of age there were no significant differences in percentage of antipoliovirus titres ⩾ 1:8 or geometric mean times (GMTs) between the early IPV group and the routinely vaccinated preterm group. At 3 and 7 months of age, the percentage of positive antihepatitis B titres (⩾ 1:10) and the GMT of the early IPV preterm group did not differ significantly from those of preterm controls. There was no significant difference in percentage of positive antihepatitis B titres between the early IPV group and full term controls at any time. GMTs for hepatitis B antibodies were significantly lower in the early IPV preterm group than in full term controls at 3 and 7 months of age.

CONCLUSIONS Administration of an additional dose of IPV simultaneously with routine HBV to preterm infants shortly after birth provides early protection from poliovirus and hepatitis B infection, and does not interfere with poliovirus antibody production at the age of 7 months.