ANTIBODY-RESPONSE TO HAEMOPHILUS-INFLUENZAE TYPE-B CAPSULAR POLYSACCHARIDE CONJUGATED TO TETANUS TOXOID IN PRETERM INFANTS

Objective. To evaluate the antibody response to a Haemophilus influenz ae type b capsular polysaccharide (HibCP) tetanus toroid (TT) conjugat e vaccine (HibCP-TT) in preterm infants. Subjects. Thirty-five healthy preterm infants with gestational ages (GA) from 27 to 36 weeks and bi rth weights from 920 to 2550 g. Controls were 37 term infants. Methods . All infants were immunized with HibCP-TT at 2, 4 and 12 months of ag e. Antibodies to HibCP and TT were determined at each immunization and 1 month after the second and third. Results. After two doses of HibCP -TT the preterm infants with GAs less than or equal to 30 weeks (n = 8 ; mean GA 29.5 weeks) had a significantly lower HibCP antibody respons e than the preterm infants with GAs >30 weeks (n = 23; mean GA, 34.2 w eeks) (P = 0.004), who for their part had a response not significantly different from that of the term infants. After the third dose there w ere no significant differences among the groups, The response to the T T part of the vaccine showed the same pattern. Conclusion. Although th e most immature infants may show an inadequate antibody response to th e initial immunizations, many preterm infants can benefit from vaccina tion with HibCP-TT when starting immunization at the same chronologic age as term infants.