Clinical studies on efficacy and safety of an acellular pertussis vaccine in Aichi Prefecture, Japan.

Of 342 cases with pertussis notified from 1986 through 1989 in Aichi Prefecture, Japan, 331 (96.8%) were unimmunized children. To confirm the clinical efficacy of the acellular pertussis vaccine combined with diphtheria and tetanus toxoids (ACP-DT i.e.) used in the mass immunization, a prospective household case contact study has been conducted since 1983. Of 56 unimmunized children, 48 developed clinically diagnosed pertussis, and of 80 children who received recommended doses of the vaccine, only four contracted the disease after the household exposure. There were no serious systemic adverse reactions including high fever, encephalopathy, shock or death attributable to the mass immunization with ACP-DT. Severe local reactions occurred in 2.5/100,000 recipients of a third and fourth dose of the vaccine during 1984-1989.