The ability of different Haemophilus influenzae type b conjugate vaccines to induce immunologic memory was compared in 381 infants who were vaccinated with one of three conjugate vaccines beginning at 2 months of age. All infants were vaccinated with unconjugated type b capsular polysaccharide, polyribosylribitol phosphate (PRP), at 12 months. In each group, high antibody responses were detected by 6–9 days after vaccination. One month after receiving PRP, infants primed with PRP conjugated to the outer membrane protein of Neisseria meningitidis or PRP oligomers conjugated to the cross-reactive mutant diphtheria protein, CRM197, had twofold higher total anti-PRP antibody concentrations than did infants primed with PRP conjugated to tetanus toxoid (P <.005). After the conjugate and the PRP boost, notable differences were present among vaccine groups with respect to the magnitude of the IgG anti-PRP antibody concentrations and light chain variable region usage as determined by idiotypic analysis. Thus, each of the conjugate vaccines primed infants for the ability to evoke memory antibody responses to PRP, but qualitative and quantitative differences in priming induced by different vaccines may affect their ability to confer protection against disease.
Bibliographical noteFunding Information:
Received 21 December 1992; revised 2 April 1993. Presented in part: annual meeting of the Society for Pediatric Research. May 1992. Baltimore. Financial support: National Institutes of Health (AI-17962. -21842. -25008, and -05064 and RR-00036). The protocol was approved by the institutional review board at each study site (Dallas. Minneapolis, and St. Louis). Written informed consent was obtained from a parent or guardian of each infant. Reprints or correspondence: Dr. Dan M. Granoff, Washington V niversity School of Medicine at St. Louis Children's Hospital, One Children's Place, St. Louis, MO 63110. *Present affiliation: Division of Immunization, Centers for Disease Control and Prevention. Atlanta.