The epidemiology of pertussis in the Republic of Ireland.

Epidemiological data on pertussis in the Republic of Ireland have been gathered annually since 1941. However, no detailed analysis of these data has, until now, been carried out. Fifteen epidemics occurred between 1941 and 1989, an average of one per 3.1 years, which is similar to epidemic intervals observed elsewhere. After the introduction of a vaccine in the 1950s, annual pertussis notifications declined, from 175 per 100,000 in 1956 to 7.6 per 100,000 in 1972. Following adverse publicity in 1973, uptake of the vaccine fell to 30% in 1976. Although uptake has increased again in recent years, it has levelled out at only 40-45% and large epidemics of pertussis occurred in 1985 and 1989. At the same time, mortality from pertussis has fallen to almost negligible levels. Most cases occur in children more than one year of age. Changes in the vaccination schedule could have a major impact on the incidence of the disease in the Republic of Ireland. However, if a further decline in the incidence of the disease is to be achieved, parents have to be persuaded of the benefits of pertussis vaccination.