Type-Specific Efficacy of Acellular Pertussis Vaccine

• Two types of acellular pertussis vaccine have been used in Japan since their introduction in 1981. They are different in their antigen content and immunogenicity. To assess the type-specific efficacy of acellular pertussis vaccine commercially available in Japan, 442 households of patients with pertussis were surveyed from 1981 to 1987. The secondary attack rates in children 2 through 8 years of age were 61.3% (46/75) in unimmunized children, 7.5% (4/53) in children fully immunized by the filamentous hemagglutinin predominant type acellular pertussis vaccine, 14.3% (1/7) in children fully immunized by the pertussis toxin—filamentous hemagglutinin type vaccine, and 13.5% (7/52) in children given whole-cell pertussis vaccine. The estimated efficacy was 87.7% for the filamentous hemagglutinin predominant type vaccine and 76.7% for the pertussis toxin—filamentous hemagglutinin type vaccine in children aged 2 through 8 years. Both types of acellular pertussis vaccine were similarly effective, without any statistically significant differences, and their efficacy was not different from that of whole-cell vaccines. This survey also indicated that adults are a major source of infection, with a high secondary attack rate of 7.8% (77/987). (AJDC 1988;142:40-42)