• Acellular pertussis vaccines, which have been used in Japan since 1981, vary in antigenic constituents among manufacturers. First, to assess the immunogenicity by manufacturer and patient age, 161 children aged 3 months to 2 years were immunized by acellular pertussis vaccine from one of three Japanese manufacturers, Biken, Takeda, or Kitasato. Anti-pertussis toxin antibody responses for children immunized with Takeda and Kitasato vaccines were comparable with patients with pertussis in the convalescent stage, and anti-pertussis toxin antibody response for Biken vaccine was far higher than those of convalescing patients. Anti-filamentous hemagglutinin antibody responses for the children given the three vaccines were far higher than those of the patients. Weak serotype 1.3 agglutinin responses were observed only in children administered the Takeda vaccine. Comparing these antibody responses among various age groups, the immunogenicity of acellular vaccines in children aged 3 to 6 months was comparable with children aged 2 years. Second, to assess the manufacturer-specific efficacy, 495 households of patients with pertussis were surveyed from 1981 to 1988. The estimated efficacy of the acellular pertussis vaccines in children aged 2 to 8 years was 82%, and there were no major differences in the secondary attack rates among children immunized with acellular pertussis vaccine from each manufacturer, ie, 12.5% (1/8) for Biken, 11.1% (2/18) for Takeda, and 5.9% (1/17) for Kitasato. We conclude from these two studies that similar efficacy was observed in children aged 2 years or older for acellular pertussis vaccines from the three manufacturers, which produced anti-pertussis toxin antibody responses comparable with patients with pertussis and far higher antifilamentous hemagglutinin antibody responses than in the convalescing patients, and that age did not affect the immunogenicity of acellular vaccines.