IMMUNOGENICITY OF HEPATITIS-B VACCINE IN PRETERM INFANTS

Objective. To determine the immunogenicity of hepatitis B vaccine in p reterm infants when the first dose of vaccine is delayed until hospita l discharge. Methods. One hundred two preterm infants (23 to 36 weeks' gestational age) born to hepatitis B surface antigen-negative mothers were enrolled. Immunization was initiated just before hospital discha rge with subsequent doses 1 and 6 months later. Serum specimens were o btained before the administration of each vaccine dose and 3 months af ter the last dose and were tested for antibody to hepatitis B surface antigen (antiHBs). Results. Eighty-seven infants (85%) completed the s tudy. Ninety percent (n = 78) of infants who completed the study seroc onverted (antiHBs greater than or equal to 10 mIU/mL); 10% (n = 9) rem ained seronegative at study completion. The geometric mean antibody ti ter to hepatitis B surface antigen for infants who seroconverted was 2 00 mIU/mL. Nonresponders (NR) differed from responders (R) in birth we ight (NR = 2090 g, R = 1560 g) gestational age (NR = 33 weeks, R = 31 weeks), and weight gain before vaccine initiation (NR = 244 g, R = 633 g). There were no differences in weight or age at vaccine initiation, Apgar scores, interval between vaccine doses, or bacterial infections , steroid use, or transfusions before vaccine initiation. Conclusions. Ninety percent of preterm infants responded to hepatitis B vaccine wh en the first dose of vaccine was delayed until hospital discharge. Non responders were more likely to be preterm infants of higher birth weig ht and higher gestational age, and to have gained less weight before v accine initiation.