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It is estimated that at 30 June, 1959—about midway point of the poliomyelitis season in
1959—66 per cent, of children aged 0-16 years had received two injections of poliomyelitis
vaccine. Applying this percentage to the child population at risk gives the following
incidence rates for the paralytic form of the disease:
Population
0-14 years
Cases
Cases per 1,000
population at risk
Vaccinated 426,000 24 0-056
Not vaccinated 219,000 89 0-406
Thus the incidence rate in the unvaccinated children was about seven times that in the
vaccinated. This is probably an understatement of the difference because among the
vaccinated cases there were five who had received only one injection and can therefore be
regarded as incompletely vaccinated.
In a similar analysis for the last six months of 1958, when approximately 45 per cent,
of the child population had been vaccinated, the corresponding differential between the
incidence rates in the unvaccinated and vaccinated was five times. The improvement in
1959 may be linked with the fact that by the end of that year slightly over one-half of the
vaccinated child population had received a third injection of vaccine.
It was not thought worthwhile to extend this analysis to the older age groups because of
the difficulty in arriving at an estimate of the 'exposed to risk' population of vaccinated
persons, as it is not known how many London adult residents have been vaccinated outside
the county.
Whooping Cough—There was a slight rise in the number of notifications of whooping
cough from 1,595 in 1958 to 1,607 in 1959. The figures for the last two years are considerably
lower than in the preceding years. Although it is known that whooping cough is
grossly under-reported, there is no reason to assume that the degree of under-notification
has suddenly changed, and one is therefore led to believe that the incidence of the disease
has in fact declined.
It would not be unreasonable to associate this decline in some degree
with whooping cough immunisation, in view of the fact that during the last few years
about two-thirds of infants under the age of one year have been given a course of whooping
cough vaccine.
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