Japan's experience in pertussis epidemiology and vaccination in the past thirty years.

The 30 years between 1949-1979 cover the stages of post-war pertussis epidemics, required notification, required vaccination, regulation of the vaccine and public reaction against adverse reactions to pertussis vaccine. The disease, called "Hyakunichi-zeki" or cough lasting 100 days, rose and fell cyclically in Japan as it did in the West. Pertussis, a notifiable disease, was reported at about 150/100,000 in 1949-50. Probably the actual case rate is 10 times higher. The Preventive Vaccination Law was in effect nationwide in 1950, causing a decline in cases to a minimum of 0.2/100,000 in 1971. As effective antibiotics for secondary infection appeared, the minimum death rate was registered as 2 nationally in 1972. Most cases occur in July and August in unvaccinated children under 5 years old. The 1st 2 deaths from DPT vaccines, in 1974 and 1975, from encephalopathy and shock respectively, prompted temporary cessation of vaccination. Consequently, public acceptance of the vaccine decreased, and both case rate and antibody prevalence rose. 61 encephalopathy deaths and 18 shock deaths due to the vaccine were reported from 1952-1974, but this figure is probably low. Japan's standards for pertussis vaccine, controlled by the Japanese NIH, reflect those of WHO. Details of government regulation of vaccine standards, as well as research up to the late 1970s for finding a purer, safer and effective pertussis vaccine are reviewed briefly. It is unknown whether the protective antigen is identical or separate from toxic components of the organism. Although some improvements in vaccination schedules and vaccine purity have been made, a more potent and less toxic vaccine is needed.