The objective of this study was to assess whether the antibody response in former extremely premature (PT) children after the primary series of immunizations is sustained after the 12 - 18 mo booster vaccines. Thirty-three 3-4 yr old children, (16 former PT [<29 wks, <1000g at birth] and 17 former fullterm [FT] infants) who received the full complement of the primary series and first booster of diphtheria-tetanus-pertussis (DPT) and H. influenzae type b oligosaccharide-CRM197- conjugated (HbOC) vaccines at the recommended chronologic ages. The PT children received enhanced potency inactivated polio vaccine at 2 mo and oral polio vaccine at 4 and 18 mo. All FT children received oral polio vaccine. Nine PT children and 14 FT children received the Hepatitis B vaccine series. Serum was obtained at 3-4 years of age for anti-tetanus toxoid (TT), Haemophilus b polysaccharide(HbPs), Diphtheria (Diph), Pertussis FHA (Pert), Hepatitis B (Hep B) and polio neutralizing antibody assays. Both the PT and FT children had similar geometric mean titers (GMT) for anti-TT, Diph, and Pert antibodies with 100% of children having protective levels. PT children had lower GMT of HbPs antibody than FT children (1.00 vs 1.66 μg/ml; p=.009). If the protective level of antibody was defined as ≥1.0 μg/ml, 50% of the PT and 88% of FT were protected (p=.003). However, 100% of PT and 94% of FT children had anti-HbPs titers ≥0.15 μg/ml. The GMTs of neutralizing antibodies to polio serotypes 1 and 2 were similar with 94%-100% protection in both groups. Fewer PT than FT children, (75% vs 100%; p=.04), had protective titers to polio serotype 3. Similar numbers of PT and FT children (77% vs 71%), had protective titers to Hep B. PT children immunized at the recommended chronological age displayed responses at 3-4 yrs of age similar to FT children for Diph, Pert, TT, HbPs (≥0.15 μg/ml), Hep B, and polio serotypes 1 and 2. Responses to polio serotype 3 were less robust than those of FT children.
Supported by University of Rochester Clinical Research Center Grant.
