Statistical studies in immunity : smallpox and vaccination / by John Brownlee.

  • John Brownlee
Date:
1905
Catalogue details

Licence: In copyright

Credit: Statistical studies in immunity : smallpox and vaccination / by John Brownlee. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    to the factors before mentioned. Unfortunately there is a complete absence of statistics referring to this matter, so that an examination of the relative influences of these different factors is impossible. The effect of revaccination on the age incidence of persons suffering from smallpox can be more readily estimated. When performed in the absence of an epidemic, or when slight outbreaks only of this disease are present, there is not a sufficient amount done to influence statistics much one way or another. In Sheffield, for instance, when the great epidemic of 1887 occurred, about five to seven per cent, of the population at each age period above fifteen years were found to be revaccinated. When, how- ever, as in this epidemic in Sheffield and in the late epidemics in Glasgow revaccination is performed on a large scale, it is found that a much larger propor- tion of persons between ten and twenty years of age avail themselves of this means of protection than at higher ages. The effects of this on later epidemics are obviously, (1), if the second epidemic occurs within a few years of the first to raise the mean age; and (2), if the later epidemic occur about fifteen years there- after to lower the mean age of attack. Revaccination, however, as a rule only begins to have an important modifying effect on the epidemic concerned when it is naturally approaching its end. The change in the age incidence of smallpox just discussed is one ^which not only applies to the vaccinated as a class, but equally to the different groups comprehended in this class. Persons suffering from smallpox are for the purpose of classification commonly divided into groups as they present on their arms one, two, three, and four or more vaccinal cicatrices. In each of these groups the mean age has steadily risen. Now with regard to the group of those who present one cicatrix this is to be expected. Since 1870 persons vaccinated in this manner have been becoming progressively fewer and fewer, and consequently in London the bulk of those presenting one vaccinal cicatrix must consist of persons at the higher ages. Exactly the same change in the mean age, however, is found to be among the members of the group presenting one cicatrix in Glasgow, although no such change in the method of vaccination has taken place there. With regard to the group, however, of persons with four or more scars, year by year since 1870 a larger and larger number of such have come into existence at lower ages and consequently it would be expected that the mean age among this group would be at any rate stationary if not lower. This is not found to be the case. The annexed table exhibits the change in the mean age which has taken place in London since 1870. The rise noted in the mean age of persons with four marks TABLE II. Mean Age of Cases and Deaths in the Epidemics in London, 1870—1902. One Scar Two Scars Three Scars Four Scars Cases Deaths Cases Deaths Cases Deaths Cases Deaths 1870-83 21-8 26-2 21-0 25-1 18-1 24-0 17-0 24-8 1892-96 26-8 35-3 29-5 43-9 26-5 31-7 23-2 .35-7 1902 34-2 39-6 34-0 41-3 31-0 37-7 27-2 34-5 40-2
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