Haemophilus influenzae type b anticapsular antibody responses to PRP-pertussis and PRP-D vaccines in Alaska native infants.

To evaluate immune responses in Alaska Native infants at high risk for invasive Haemophilus influenzae type b (Hib) disease, we studied PRP-pertussis and PRP-D conjugate vaccines in this population relative to responses in white infants in California and New York. Infants were immunized at two, four, and six months of age (both vaccines). In the PRP-pertussis trial, there were no significant differences in antibody levels at any age between Alaska Native infants and infants from California. Only 50% of the infants had a twofold or greater antibody rise after three doses. In the PRP-D trial, antibody levels at two months of age (presumably maternally acquired) were significantly higher for Alaska Native infants compared with infants from New York (P = .002). There were no significant differences in antibody levels after any of the three doses. Among Alaska Native infants there was no significant difference in antibody response based upon degree of ethnic purity.