COMPARISON OF A 3-COMPONENT ACELLULAR PERTUSSIS-VACCINE WITH A WHOLE-CELL PERTUSSIS-VACCINE IN 15-MONTH-OLD THROUGH 20-MONTH-OLD INFANTS

Objective. To compare the immunogenicity and reactogenicity of a dipht heria and tetanus toxoids and three-component acellular pertussis vacc ine (DTaP) with a diphtheria and tetanus toxoids and whole-cell pertus sis vaccine (DTwP) when administered as a booster dose to infants 15 t hrough 20 months of age. Design. Randomized, double-blind, comparative study. Setting. Three pediatric practices (two private; one hospital- based). Participants. One hundred and sixty-five healthy 15-through 20 -month old infants. Selection procedures and interventions. Infants we re randomly assigned in a 2:1 ratio to receive vaccine from a single l ot of DTaP or from commercially available DTwP. DTaP contained 25 mug of pertussis toxoid, 25 mug of filamentous hemagglutinin, 8 mug of per tactin (69-kilodalton outer membrane protein), 25 flocculating units o f diphtheria toxoid, and 10 flocculating units of tetanus toxoid per 0 .5-mL dose. DTwP contained one half the concentrations of diphtheria a nd tetanus toxoids compared with DTaP and a pertussis component with a potency of 4 U/0.5-mL dose. Serum samples were obtained on the day of immunization and 4 weeks later. Adverse reactions were recorded by pa rents for 7 days after immunization. An interval history was obtained 4 weeks after immunization. Measurements and results. IgG antibody to pertussis toxoid, filamentous hemagglutinin, pertactin, diphtheria tox oid, and tetanus toxoid was measured by an indirect enzyme-linked immu nosorbent assay (ELISA) method. One month after immunization, the geom etric mean antibody levels after DTaP compared with DTwP were: pertuss is toxoid, 70.6 vs 28 ELISA U/mL (P = .003); filamentous hemagglutinin , 183.4 vs 43 ELISA U/mL (P < .001); pertactin, 216 vs 49.9 ELISA U/mL (P < .001); diphtheria, 14.1 vs 14.9 IU/mL (P = .74); and tetanus, 11 .9 vs 14.8 IU/mL (P = .089). After immunization with DTaP, most local and systemic adverse experiences were significantly fewer compared wit h DTwP (P < .05). Conclusions. This three-component DTaP vaccine demon strates significantly greater immune responses to pertussis toxoid, fi lamentous hemagglutinin, and pertactin, equivalent immune responses to diphtheria and tetanus toxoids, and significantly less reactogenicity compared with a licensed DTwP.