Acellular pertussis vaccination of 2-month-old infants in the United States.

This is the first study in children from the United States that evaluates the immunogenicity of and adverse reactions to the Connaught/Biken two-component acellular pertussis vaccine compared with whole-cell pertussis vaccine when given as a primary immunization series at 2, 4, and 6 months of age. Three hundred eighty infants were studied; 285 received acellular diphtheria-tetanus toxoids-pertussis (DTP (ADTP)) and 95 received whole-cell DTP (WDTP). Following the third dose, ADTP vaccination produced higher antibody responses than WDTP to lymphocytosis-promoting factor (enzyme-linked immunosorbent assay IgG geometric mean titer (GMT) = 131 vs 9 and Chinese hamster ovary cell assay GMT = 273 vs 16) and to filamentous hemagglutinin (IgG GMT = 73 vs 10) (all P less than .0001). Agglutinin responses were higher in WDTP compared with ADTP recipients (GMT = 50 vs 37; P = .02). Local reactions were fewer for all three doses following ADTP vaccination. Fever, irritability, drowsiness, anorexia, vomiting, and unusual crying all occurred less frequently in ADTP compared with WDTP recipients for one or more of the three doses. We conclude that this two-component ADTP vaccine when given as a primary series produces greater immunogenicity and fewer adverse effects than the currently licensed WDTP vaccine.