Factors associated with superior antibody responses to a single dose of Haemophilus influenzae type b-tetanus toxoid conjugate vaccine administered to Chilean infants at 2 months of age.

The anticapsular antibody response of Chilean infants to a single dose of Haemophilus influenzae type b capsular polysaccharide-tetanus toxoid conjugate, vaccine is substantially higher than that observed among infants of similar age from the USA. Comparison of selected demographic and environmental factors indicates that low maternal education and a greater number of persons in the home are significantly associated with the superior responder phenotype. High anticapsular antibody responses were associated with high antibody responses to tetanus toxoid, the carrier protein in this conjugate, but not to diphtheria toxoid. These data suggest that environmental factors may enhance the magnitude of the primary antibody response to PRP-T vaccine.