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11
Dr. Buchanan considers that the following lessons may be learnt
from the above Table :—
1. "The vaccinated are much less liable to die of small-pox than
the unvaccinated.
2. "Vaccination is not an absolute protection against small-pox.
In recording the present illustration of a quite admitted fact, it will
be convenient to refer to the possibility of difference in the degree of
protection afforded by vaccination now-a-days as compared with
former times." The data with which we are furnished do not enable us
to form an entirely correct opinion as to the greater protection afforded
by vaccination at an early period after its introduction, yet there is
reason for believing that the protective influence of vaccination was
greater in the beginning of this century than it is at the present time.
In an Address on Micro-Organisms and Diseases, which Dr.
Cameron, M.P., the President of the Health Department of the
Social Science Congress, delivered at the Meeting which was held in
Dublin, in October, 1881, remarked that, "whilst comparing the
results of vaccination as performed in Dr. Jenner's time and in the
present time, although the operation was not then so carefully performed
as it now is, yet the protection conferred, as measured by the
death-rate in cases of small-pox occurring in vaccinated persons, was
ten times more efficient than that secured by the most complete form
of vaccination practised at the present day, and twenty-five times
greater than that afforded by our vaccination, good, and indifferent,
as at present practised."
Dr. Cameron accounts for the falling off in results by "a deterioration
of the vaccine virus." In Dr. Jenner's time, one vaccination was
deemed a sufficient protection during life, but now-a-days it is considered
necessary to repeat the operation two or more times for the
protection of the individual. Vaccination, however, still affords a
great protection against small-pox, as is shown from the figures above
tabulated by Dr. Buchanan, from which it appears that the degrees
of protection, both actual and relative, afforded by vaccination, is
greatest to people under 5 years of age; less when ages from birth to
20 years are examined; and still less when people of all ages are
taken into account.