Children with a tendency to eczema are prone to suffer an outbreak of that disease as the result of vaccination. In Jenner's time, indeed, it was considered not only that there was great risk of causing an aggravation of any slight eczematous eruption by vaccination, but that the mere existence of the eczema, even in the most trivial form, was likely to interfere with the success of the vaccinal inoculation. This has been the general feeling of the profession. Quite recently, however, many observations have been recorded tending to show that the old dread of vaccinating an eczematous child was not altogether warranted. The question needs further study, and, while it is probably best to postpone the operation under ordinary circumstances, nothing should induce us to withhold its protective influence where there is any manifest danger of actual exposure to small-pox.
Although eczema is the most common of the cutaneous affections called forth or aggravated by vaccination, there are various forms of skin disease, some of them difficult to classify, that occasionally result. They are usually vesicular, pustular, or furuncular—that is to say, irritative. In the majority of instances it will be found either that the pock itself has followed an irregular course, being whitish, diffuse, and ending in an exaggerated although superficial incrustation, or that it has been subjected to injury. Still, in some cases neither of these conditions is the precursor of the skin affection. In many instances the latter can only be called nondescript. There seems to be some occult connection between vaccination and the curious skin disease described by the late Tilbury Fox of London under the name of impetigo contagiosa; and, indeed, Piffard of this city has found certain microphytes to be common to the crusting period of vaccinia and that of contagious impetigo. What the relation of the two affections is to each other, however, it is difficult to say.
Apart from impetigo contagiosa, the cutaneous complications that follow in the wake of vaccination possess no distinctive features, and their management differs in no wise from that of the same manifestations due to other causes.
THE TECHNICS OF VACCINATION.—This aspect of our theme involves a number of separate considerations. It will be convenient to give our attention first to the matter of the choice of virus. The question arises at once as to the selection between animal vaccine and the humanized variety. In a broad sense the term animal vaccine includes—1. Virus derived directly from a case of so-called spontaneous cow-pox. 2. Variola vaccine—i.e. the virus of an affection of the cow resulting from variolation. 3. The virus of horse-pox (not strictly vaccinal). 4. Retro-vaccine—i.e. the virus of an affection produced in the cow by the inoculation of vaccinia from the human subject. 5. The virus of a disease (true vaccinia) propagated through a series of bovine animals from the so-called spontaneous cow-pox, being the virus now commonly understood by the term, and the variety here referred to when it is not stated to the contrary.
By humanized vaccine we understand that which is obtained from the human subject, no matter how short or how long its descent from the cow. As regards animal vaccine, we may practically exclude from consideration all but the last variety mentioned, that being the one to which, in the great majority of instances, the term is now restricted. This narrows the question down to the choice between virus that has been propagated through a number of bovine animals (practically, calves) from the spontaneous disease in the cow, and that which, whatever its original source, has already passed through the human system.
The variety first mentioned, sometimes called primary vaccine, is generally spoken of by authors as not very trustworthy as regards its infective power (that is, not to be counted on to take), and as prone to give rise to undue inflammatory complications when its use does prove successful. These unpleasant qualities might be explained by the supposition that primary vaccine is not apt to be at its best when it is now and then obtained. Practically, however, it may be dismissed without further consideration, for it is seldom to be had.
The second form—variola-vaccine—is manifestly improper to be used whenever genuine vaccine is to be obtained, unless, indeed, we shut our eyes to the accumulating evidence that variola-vaccine, so called, is not vaccine at all. Furthermore, it is a question whether its use, as well as all attempts to produce it, should not be forbidden by law.
The third variety, if such it may be called, it does not seem legitimate to use in the present state of our knowledge, since it is not yet proved satisfactorily that horse-pox possesses the full protective power of cow-pox, or is free from objections that do not arise in connection with the latter.
As to retro-vaccine, while the writer is unable to see any positive reason against its use, neither can he see any reason why it should be superior to humanized vaccine, as such, save that during the period of its bovine propagation it is not liable to become contaminated with the poison of syphilis. The idea that an enfeebled stock of humanized vaccine can have new life infused into it by passing through the system of the cow is not reasonable primâ facie, and there are no particular facts to support it. By ensuring freedom from the danger of communicating syphilis retro-vaccination doubtless served a good purpose at one time, but now, since the remarkable and enduring excellence of the Beaugency stock is so well established, there seems to be no excuse for a further resort to the practice.
The last of our five forms of animal vaccine, that produced by the continued propagation of spontaneous cow-pox through calves, is what is now known as animal vaccine par excellence. Its advantages over the other forms are so obvious that it alone should figure in any comparison between animal and humanized vaccine. That being understood, what are the relative merits of animal and humanized vaccine? It should be stated, in the first place, that bovine virus should be compared with virus that has long been humanized, for lymph of but a few removes from the bovine animal does not show any noteworthy differences from animal vaccine itself.