Whether polio immunization was accomplished with IPV or OPV did not significantly influence the antibody responses in sera obtained at 7 months of age for anti-PRP, anti-diphtheria and anti-tetanus toxoid antibodies and antibodies to pertussis antigens, when DTaP/PRP-T was given in the primary series.

We compared the antibody response to Haemophilus influenzae type b capsular polysaccharide (PRP) after 1, 2, or 3 doses of a diphtheria-tetanus toxoids-acellular pertussis (DTaP) vaccine combined with a PRP-tetanus conjugate (PRP-T) vaccine, followed by separate injections of DTaP and PRP-T vaccines for the last 1 or 2 doses. Healthy infants were recruited from pediatric practices and were immunized according to recommended schedules. A significant decrease in the mean anti-PRP (from 5.25 to 2.68 microg/mL) and anti-tetanus toxoid antibody responses (from 0.13 to 0.09 Eq/mL) was observed as the number of doses of the DTaP/PRP-T combination vaccine increased (P<.02 and P=.01, respectively). In contrast, the mean anti-diphtheria toxoid antibody response increased with increasing numbers of DTaP/PRP-T doses (P=.0001). The effects of interference were not eliminated by the completion of the primary series with 1 or 2 doses of the DTaP and PRP-T vaccines given separately.

Eight healthy adults and 48 infants 2 and 4 months old were immunized with Haemophilus influenzae type b-Neisseria meningitidis outer membrane protein complex conjugate vaccine (PRP-OMP) to evaluate antibody kinetics in the first days after immunization. Five adults (63%) had some decrease in antibody, although the geometric mean did not decrease significantly. With one exception, the nadir occurred on postimmunization day 3. Seven had an antibody increase by day 7. Of the children, 6 (75%) of 8 and 17 (77%) of 23 had a decrease in antibody in serum obtained on day 2-3 after the first or second dose, respectively, the magnitude of which directly correlated with the preimmunization antibody concentration. However, the geometric mean did not decrease significantly. Within 1 week of immunization, 85% of infants had an increase in antibody, significantly greater after the second dose than after the first. A high concentration of maternally derived antibody before immunization correlated negatively with antibody response. Thus, a transient decrease in antibody occurs in most adults and infants 2-3 days after immunization with PRP-OMP followed by a prompt increase by day 7.

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