Efficacy of an acellular pertussis vaccine in Japan.

To assess the efficacy of an acellular pertussis vaccine that has been used in Japan since 1981, 283 patients with pertussis were selected among patients with suspected pertussis seen at hospitals located around the Tokyo Metropolitan area from 1981 to 1983. The survey of secondary cases in household contacts showed that attack rates in children 0 to 6 years of age were 73.1% in unimmunized children, 15.0% in those fully immunized by whole-cell vaccines, and 15.4% in those given acellular vaccines. The efficacy of Japanese acellular pertussis vaccines was 79% and was not different from that of whole cell vaccines.