THE AGGLUTININ RESPONSE TO WHOLE-CELL AND ACELLULAR PERTUSSIS VACCINES IS BORDETELLA-PERTUSSIS-STRAIN DEPENDENT

Objective.-To determine the significance of the Bordetella pertussis strain used as the antigen in the agglutinin assay for the evaluation of pertussis vaccines. Design.-Randomized, double-blind study. Setting.-Health maintenance organization clinics, primary care clinic at a referral hospital, and private practices in Los Angeles County, California. Participants.-Forty healthy infants. Selection Procedures.-Convenience sample. Interventions.-Twenty infants received whole-cell pertussis-component diphtheria-tetanus-pertussis vaccine (DTP), and 70 infants received acellular pertussis-component diphtheria-tetanus-pertussis vaccine (APDT) at ages 2, 4, and 6 months. Measurements.-The agglutinin assay was performed using three separate B pertussis strain preparations: (1) strains 1 30 and 138 in equal quantities, the constituents of the DTP vaccine, (2) strain 460, and (3) strain Tohama, the constituent of the APDT vaccine. Results.-The agglutinin titers were highly strain dependent; in both groups of vaccinees at both ages the Tohama values were highest, followed by strain 460 and then strains 130/138. The vaccine groups had comparable titers at age 2 months regardless of the assay antigen used. However, at age 7 months, after three immunizations, the DTP group geometric mean titer was more than 10 times greater than that of the APDT group using strains 130/138, but only 2.6 times higher using strain 460 and almost equivalent using Tohama strain. Conclusion.-Vaccine group agglutinin value comparisons strongly depend on assay antigens used.