In applying to cow-pox the term “variolae vaccinae,"
Jenner gave expression to his belief that this disease was in
reality nothing more nor less than small-pox of the
cow. But soon it was discovered that if there were
such a malady as “small-pox of the cow,” there
was also, as Dr Loy first satisfactorily demonstrated,
Relationship of small-pox and cow-pox.
a small-pox of the horse, which, under the name of
“grease,” was resorted to from time to time as a source
of vaccine lymph. Jenner had, indeed, put forward the
suggestion that “grease” was a necessary antecedent to cowpox;
but even taking this term to have been used by him in
the sense of horse-pox, he was, in all probability, mistaken
in his assumption. At the same time, however, there can be
little doubt that these two diseases are very closely allied,
if indeed they be not identical. As evidence of a definite
relationship between human small-pox and cow-pox, it may
be mentioned that whereas, prior to the introduction of vaccination, epidemics of these disorders frequently arose concurrently,
the so-called “natural” cow-pox has now in great
measure disappeared. There is, moreover, no appreciable
difference in the minute anatomical appearances characteristic
of the eruption following on inoculation of one or other of these
two affections in the human subject. But of far greater importance
in this connexion are the results obtained by numerous
observers who, in various parts of the world, and almost from
the time of lenner onwards, have set themselves the task of
attempting, by experimental methods, to solve the problem
of the true relationship of variola to vaccinia. As the outcome
of this work it may now be definitely stated that small-pox
lymph, more especially, as the present writer has shown, if
obtained from the primary vesicle of a case of the inoculated
form of the disease, by passage through the system of the calf
can be so altered in character as to become deprived of its
power of causing a generalized eruption, while inducing at the
site of inoculation a vesicle indistinguishable from a typical
vaccine vesicle; and, more important still, that when transferred
again to man, it has by such treatment completely lost
its former infectious character. Such being the case, it may
fairly be asserted that cow-pox, or rather that artificially
inoculated form of the disease which we term vaccinia, is nothing
more nor less than variola modified by transmission through
the bovine animal. An outbreak of small-pox, indeed, may
be turned to account for raising, by appropriate experimental
methods, a fresh stock of vaccine lymph.
There is much evidence to prove that the results following on vaccination are due to a specific contagium, and, moreover, that the particular micro-organism concerned is capable of existing, during one period of its life-cycle, in a resting or spore form, in which condition it is more resistant to the germicidal effects of glycerin than is the case Bacteriology. with non-sporing microbes. Advantage is taken of this fact, in the method devised by the present writer, and now -employed officially in England, as also on the Continent and in America, for ensuring the bacteriological purity of vaccine lymph. Up to the present, unfortunately, no satisfactory method has been discovered by which the micro-organism of vaccinia can be unfailingly cultivated on artificial media while still retaining its specific properties.
The publication in 1896 of the final report of the English Royal Commission on Vaccination, in which the various phases of the vaccination question are discussed on the basis of evidence obtained from witnesses of all shades of opinion during a period extending over no less than six years, considerably simplifies the task of dealing with this subject. The Vaccination Commission, 1889–96. Royal Commission, originally numbering fifteen members,[1] with Lord Herschell as president, was appointed in May 1889, the terms of reference being as follows: “To inquire and report as to—(1) The effect of vaccination in reducing the prevalence of, and mortality from, small-pox. (2) What means, other than vaccination, can be used for diminishing the prevalence of small-pox; and how far such means could be relied on in place of vaccination. (3) The objections made to vaccination on the ground of injurious effects alleged to result therefrom; and the nature and extent of any injurious effects which do, in fact, so result. (4) Whether any, and, if so, what means should be adopted for preventing or lessening the ill effects, if any, resulting from vaccination; and whether, and, if so, by what means, vaccination with animal vaccine should be further facilitated as a part of public vaccination. (5) Whether any alterations should be made in the arrangements and proceedings for securing the performance of vaccination, and, in particular, in the provisions of the Vaccination Acts with respect to prosecutions for non-compliance with the law.”
The evidence given before the Royal Commission was published at intervals in a series of Blue-books, but, as stated, it was not until August 1896 that the final report made its appearance. As regards the effect of vaccination in reducing the prevalence of, and mortality from, small-pox, the following conclusions were arrived at, Dr Collins and Mr Picton alone dissenting: “(1) That it diminishes the liability to be attacked by the disease. (2) That it modifies the character of the disease and renders it (a) less fatal, and (b) of a milder or less severe type. (3) That the protection it affords against attacks of the disease is greatest during the years immediately succeeding the operation of vaccination. It is impossible to fix with precision the length of this period of highest protection. Though not in all cases the same, if a period is to be fixed, it might, we think, fairly be said to cover in general a period of nine or ten years. (4) That after the lapse of the period of highest protective potency, the efficacy of vaccination to protect against attack rapidly diminishes, but that it is still considerable in the next quinquennium, and possibly never altogether ceases, (5) That its power to modify the character of the disease is also greatest in the period in which its power to protect from attack is greatest, but that its power thus to modify the disease does not diminish as rapidly as its protective influence against attacks, and its efficacy, during the later periods of life, to modify the disease is still very considerable. (6) That re-vaccination restores the protection which lapse of time has diminished, but the evidence shows that this protection again diminishes, and that, to ensure the highest degree of protection which vaccination can give, the operation should be at intervals repeated. (7) That the beneficial effects of vaccination are most experienced by those in whose case it has been most thorough. We think it may fairly be concluded that where the vaccine matter is inserted in three or four places, it is more effectual than when introduced into one or two places only, and that if the vaccination marks are of an area of half a square inch, they indicate a better state of protection than if their area be at all considerably below this.”
For the evidence, statistical or otherwise, on which these conclusions are based, the Reports of the Royal Commission should be consulted. But reference may here be made to two facts of which proof is overwhelming. (1) Small-pox, in pre-vaccination days a disease of infancy and childhood—like measles at the present day—has in the United Kingdom become a disease mainly of adults. The shifting of age-incidence can only be accounted for by the custom of vaccination in infancy. To this day, when small-pox attacks young unvaccinated children, it is found to be as virulent as, or even more virulent than, small-pox in the unvaccinated at higher ages. On the other hand, small-pox is practically unknown among well-vaccinated children. When, quite exceptionally, such children have been attacked, the disease has been so trivial in character as to be liable to escape recognition altogether. (2) Medical men, nurses and other persons exposed to the disease habitually protect themselves by efficient re-vaccination, and when this precaution has been taken, never contract small-pox.
The clinical activity and bacteriological purity of the lymph employed for vaccination; the skilful performance of the operation itself; the making an adequate number of insertions of lymph over a sufficient area; the observance of precautions needful for ensuring strict asepsis, both at the time of vaccination and subsequently Efficient vaccination. until the vaccination wounds are soundly healed—all these are matters to be regarded as essential to “efficient vaccination.” Certain principles in respect of them are generally recognized, and in the case of public vaccinators, whose work comes under government inspection, a series of instructions on these several points are prescribed by the Local Government Board. First in regard to lymph. That which is now almost universally employed in Great Britain is glycerinated cali lymph, the use of which has entirely superseded, in public vaccinations, the arm-to-arm method which for many years previously had been employed as the best means then attainable
- ↑ The original Commissioners were—Lord Herschell, C. Bradlaugh, Dr Bristowe, Dr Collins, Sir C. Dalrymple, J. S. Dugdale, Q.C., Prof. M. Foster, Sir E. H. Galsworthy, Sir Guyer Hunter, J. Hutchinson, Sir James Paget, J. A. Picton, Sir William Savory, S. Whitbread, F. Meadows White, Q.C. Mr Bradlaugh, Dr Bristowe and Sir William Savory died during the progress of the inquiry. Only one of the vacancies thus caused was lled up, Mr J. A. Bright having been appointed on the death of Mr Bradlaugh.
