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The general picture of incidence shown in figure 2 is reminiscent of what happened to
diphtheria incidence before and after the beginning of the immunisation campaign.
The incidence of poliomyelitis from 1947 to 1958 varied greatly from year to year, between
100 and 1,000 cases occurring each year. With the coming of Salk vaccination the relationship
between the disease and the immunity of the population was altered until a progressive
decline in incidence set in. A roughly ten-fold decline took place between 1959 and 1962.
In the following year an acceleration of this trend occurred as the widespread use of oral
vaccine, by reducing the number of disease carriers in the population, brought benefit to
vaccinated and unvaccinated alike.
Smallpox—No cases of smallpox were notified during the year.
Whooping cough—There was a rise in the number of notifications of whooping cough to
2,601 from the unusually low figure of 619 in 1962. The mildness of the disease is shown by
the fact that only two deaths resulted. A number of very mild attacks of whooping cough
in recent years have come as a result of the modification of the disease by vaccination in
the past. Such attacks have become so frequent and so mild in schoolchildren as to necessitate
a revision of the rules on exclusion from school by reason of whooping cough.
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