Immune response of premature infants to meningococcal serogroup C and combined diphtheria-tetanus toxoids-acellular pertussis-Haemophilus influenzae type b conjugate vaccines

To determine the immune response of premature infants to meningococcal sero group C capsular polysaccharide (MCC) and combined diphtheria-tetanus toxoi ds-acellular pertussis-Haemophilus influenzae type b (DTaP-Hib) conjugate v accines, 105 infants born at, <32 weeks' gestation had Hib IgG geometric me an concentrations (GMCs) and MCC serum bactericidal antibody (SBA) geometri c mean titers (GMTs) measured 1 month after the third immunization. Term in fants served as control subjects. Premature infants had Hib GMCs of 0.27 <m u>g/mL, with 21% achieving GMCs. >1.0 mug/mL, compared with 0.81 mug/mL and 46% in term infants (P < .001 and P = .003, respectively). The MCC SBA GMT was 398, with 99% achieving an SBA <greater than or equal to>8, compared w ith 380 and 98% in term infants (P = .84 and P = 1.0, respectively). Hib Ig G was associated with age at third immunization (P < .001). When combined w ith the DTaP vaccine used in this study, the Hib GMC of premature infants w as extremely low. The SBA GMT to MCC was similar to that of term infants.