[Whooping cough epidemiology in Chile (1950-1990). The adult as new reservoir of infection?].

The epidemiology of whooping cough is analyzed using the disease notifications in Metropolitan Region and some rural areas from 1950 to 1990. Morbidity rate tendencies show a decreasing endemic disease interrupted by irregular increases, the last in 1985. Mortality fell from 11.9 per 100,000 in 1950 (60% of deaths in boys of less than one year old), to less than 1 per 100,000 since 1967. Since 1982, all deaths occurred in less than one year old boys. Lethality was high initially, specially in rural areas but the differences with Metropolitan area decreased since 1975. Approximately 90% of notifications are in less than one year old boys. However, there is a sustained rate elevation in boys older than 10 years old, predicting the increasing importance of the infection in young adults. The described changes antedate and are intensified by the immunization program. Their relationship to the lack of compliance with the program and the vaccine efficacy are discussed.