Protective efficacy of the Takeda acellular pertussis vaccine combined with diphtheria and tetanus toxoids following household exposure of Japanese children

A systematic trial of the efficacy of the Takeda acellular vaccine for the prevention of whooping-cough (pertussis) in Japanese children is described. This vaccine does not contain intact cells, but does contain cellular fragments which have been found to spur the development of immunity. In 1947 a vaccine containing whole-cells began to be used in Japan, and by the mid 1970s the disease was well under control. Concerns regarding the safety of the vaccine, and a shift of the normal time of administration from three months of age to two years have led to a marked decrease in pertussis vaccines in recent years. Starting in about 1979, epidemics of considerable size marked by severe problems and death occurred. In 1981 a new vaccine, which did not contain whole cells and was combined with vaccine against diphtheria and tetanus, began to be used in Japan. Epidemic pertussis is again under control in Japan; however, children under the usual age of inoculation (two years of age) remain at two- to threefold risk. The occurrence of pertussis was studied among 62 vaccinated children who were exposed at home and 62 unvaccinated children who were similarly exposed. Fifteen percent of inoculated children become ill following exposure, as compared with 76 percent of the children who did not receive immunization. All of the cases of children who had been immunized were mild and were not distinguishable from other upper respiratory tract infections. The study estimates that vaccination is effective in preventing typical pertussis in 98 percent of children, and is 81 percent effective against all pertussis-like symptoms. (Consumer Summary produced by Reliance Medical Information, Inc.)