London's Pulse: Medical Officer of Health reports 1848-1972
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Hints from the Health Department. Leaflet from the archive of the Society of Medical Officers of Health. Credit: Wellcome Collection, London
London County Council 1952
[Report of the Medical Officer of Health for London County Council]
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Table 3
Poliomyelitis cases by different types of antigens by months of the year with the expected number of cases calculated from the not inoculated group.
| Month | A.P.T. | Combined | All other antigens | |||
|---|---|---|---|---|---|---|
| Observed | Expected | Observed | Expected | Observed | Expected | |
| January | — | 0.03 | 0.01 | — | 0.02 | |
| February | — | 0.05 | — | 0.02 | — | 0.01 |
| March | — | 0.07 | 1 | 0.07 | — | 0.03 |
| April | — | 0.05 | — | 0.08 | - | 0.02 |
| May | 1 | 0.68 | — | 0.89 | — | 0.29 |
| June | 2 | 1.03 | 3 | 1.27 | — | 0.51 |
| July | 3 | 1.55 | 7 | 2.48 | - | 0.76 |
| August | 3 | 1.72 | 12 | 2.60 | — | 0.71 |
| September | 4 | 1.41 | 11 | 2.29 | 1 | 0.67 |
| October | 1 | 1.94 | 3 | 0.47 | - | 0.33 |
| November | 1 | 0.76 | — | 0.16 | - | 0.17 |
| December | — | 0.22 | — | 0.04 | 1 | 0.05 |
In the early months of the year the number of cases of poliomyelitis was sporadic
and the use of any kind of rates at all based on such small data may be held to be not
justifiable. However, as poliomyelitis became epidemic in the summer months the
comparison becomes more realistic.
In the months of June and July the observed number of cases is nearly twice
the expected number for A.P.T. and more than twice as great for the combined antigen;
in August the observed number exceeds the expected by 70 per cent, for A.P.T., while,
for the combined vaccine, the observed cases are more than four times those expected ;
in September the observed cases rise to more than double the expected number for
A.P.T. and nearly five times the expected number for the combined antigen ; thereafter
both the expected number and the number of inoculated poliomyelitis cases fall rapidly.
By adding up the diagonals of Tables 1A, 1B and 1C it is possible to show the
observed and expected number in the same month as inoculation and in the three months
following inoculation separately and this is done in Table 4. The average period of
exposure to risk will be, for the same month—2 weeks ; for the first, second and third
month following inoculation—4 weeks each. Allowance has been made for the average
period of exposure of two weeks only in the calculation of the expected rates for the
cases of poliomyelitis occurring in the same month as inoculation.
It is apparent, that either for the whole year or the three summer months of high
epidemic proportions, the excess of observed cases is concentrated in the same month or