Acellular pertussis vaccines developed in Japan and their application for disease control.

Acellular pertussis vaccines, comprising mainly pertussis toxin and filamentous hemagglutinin (FHA) and used successfully in Japan since 1981, were evaluated. Anti-pertussis toxin antibody responses in children immunized with acellular pertussis vaccines were comparable or higher than in convalescent-stage patients with pertussis, while those for anti-FHA were far higher. Reactogenicity was much less than with whole cell pertussis vaccines: Fever > or = 38 degrees C occurred in 2%-4% of vaccinees; there was little redness > or = 5 cm in diameter at the vaccination site with the first dose but occurred in 7%-8% of vaccinees with subsequent doses. The estimated efficacy of acellular pertussis vaccine in children ages 2-8 years was 84% (95% confidence interval, 71%-91%). Since vaccine-induced immunity weakens after 6-10 years, adults are now a major source of pertussis transmission. The source of infection was an adult in 11.2% (10/89) of cases, and the secondary attack rate was 10.3% (19/185). Immunization with acellular pertussis vaccines for both adults and children is recommended for disease control.