At 3 to 4 years of age, former preterm and full-term children had similar geometric mean titer (GMT) values of antibodies to tetanus, diphtheria, and pertussis. Preterm children had a lower GMT value of Haemophilus polyribosylribitol phosphate (PRP) antibody than did full-term children (0.99 vs 3.06 microg/mL). Fifty percent of preterm and 88% of full-term children had PRP antibody >1.0 microg/mL; 100% of preterm and 94% of full-term children had anti-PRP titers >0.15 microg/mL. GMT values of neutralizing antibodies to polio serotypes 1 and 2 were similar, with 94% to 100% of both groups above protective levels (> or = to 1:8). The difference in GMT values of polio serotype 3 approached significance (29 vs 73); fewer preterm children had protective titer values (75% vs 100%). Among children vaccinated against hepatitis B, 75% of preterm and 71% of full-term children were protected (10 mIU/mL).Conclusions
Preterm children immunized at the recommended chronological ages displayed antibody responses similar to those for full-term children for most immunizing antigens. Responses to PRP and polio serotype 3 were less robust than those of full-term children. Pediatrics 1998;101:597-603.