If then, the first promoters of Vaccination were led, from their ardour in a cause of such vital interest to the whole human race, and before time had been allowed to afford sufficient data whereon to found a more correct opinion, to conclude that Vaccination would, in every instance, prove an absolute and infallible preventive of future susceptibility of Small Pox infection, let us not, on that account, run into an error incalculably more dangerous in its tendency, and underrate or deny altogether the degree of security which it actually affords. That this is more than sufficient to render it worthy of universal adoption, there cannot be any reasonable doubt; but it would have been strange indeed, if, in the undeviating uniformity of its effects, Vaccination had formed a single exception to the law of uncertainty that attaches to every other agent, which it has, at any time, been permitted to mankind to employ for the promotion or preservation of the health of the human constitution: and, considering the innumerable varieties which prevail in the latter, we ought rather, perhaps, to feel surprise that the influence of Vaccination over all these varieties, should have been proved to be so similar as to have justified us in considering as a general, what was at first too hastily concluded to be an absolute rule.
That the great majority of instances in which Vaccination has afforded perfect security against any future attack of Small Pox, fully warrants this conclusion, the results already detailed are sufficient to prove. What proportion these cases bear to the comparatively few, wherein the protection has been less perfect, it will not be possible to discover, because we are unable to ascertain how many hundreds of thousands or millions have passed through the vaccinating process. But little difficulty would be encountered, however, in ascertaining the full amount of the few who have had any thing bearing the slightest resemblance to an attack of Small Pox after Vaccination: these, for the most part, have been carefully recorded, and a degree of importance has certainly been attached to them greater than is warranted, either by their number, their severity, or their results.
It is of still more importance, however, to know, that when Small Pox has occurred after Vaccination, it has been so essentially altered in the severity of its symptoms, and in the degree of danger arising from it, as to have rendered it entirely harmless in almost every instance; and although fatal cases have taken place in a few insulated and peculiar examples, they have been very much more rare than those which have occurred in consequence of inoculated, or even of secondary Small Pox. Sir Gilbert Blane, after describing (p. 10-11) the mild character of the disease as occurring after Vaccination, continues thus—“What forms the strong line of distinction from proper Small Pox is, that, with a few exceptions, it does not advance to maturation and secondary fever, which is the only period of danger. I am not prepared to deny that death may have occurred in a few instances; nay, there seems sufficient evidence that it actually has; but then adverse cases are so rare as not to form the shadow of an objection to the expediency of the general practice. A few weeks ago, at a meeting of this (the Medical and Chirurgical) Society, at which forty members and visitors were present, I put the question, whether any of these eminent and extensive practitioners had met with any fatal cases of this kind. Two gentlemen had each seen a single case, and two other gentlemen took occasion to say, that they had each seen a case of second Small Pox—both of which proved fatal.” And Dr. Thomson tells us (Historical Sketch, &c. p. 279), that “since the publication of my ‘Account of the Varioloid Epidemic,’ I have seen above two hundred additional examples of Small Pox in Edinburgh, making in all eight hundred and thirty-six cases of this disease, which have come under my observation since June, 1818. Of the whole number, two hundred and eighty-one have occurred in individuals who had neither had Small Pox nor Cow Pox, and of these fully more than one in four died; seventy-one had previously passed through Small Pox, and of these two have died; and four hundred and eighty-four had undergone the process of Vaccination, and of this number one only died; results (adds Dr. Thomson) which evince, beyond the power of cavil, the beneficial effects of Vaccination in protecting the human constitution from the dangers of Small Pox, and the great advantages which must ultimately arise from the universal adoption of this practice.”—Perhaps the most fatal epidemic Small Pox, which has occurred of late years, was that which took place at Norwich in 1819. A history of it was published in the following year by Mr. Cross, and the general result was in perfect accordance with Dr. Thomson’s experience of the epidemic at Edinburgh.
Mr. Cross relates that two deaths only took place after Vaccination, and justly observes, that “these can have no weight against the practice of Vaccination compared with 10,000 vaccinated individuals, living in the midst of a contaminated atmosphere; with 530 deaths among little more than 3000 who had neglected to be vaccinated; and with the occasional occurrence of regular Small Pox in those who formerly had the disease.” Of the 10,000 persons thus protected by Vaccination, the Reviewer of Mr. Cross’s History, &c. observes (Edin. Med. and Sur. Journal, Vol. xvii. p. 127), “Had these persons been protected by variolous (Small Pox) inoculation, conducted in the best manner, and in the most favourable circumstances, at least 33 of them (1 in 300) would have died of the process intended to protect them; so that in comparing the advantages of the two methods of protection, we have to weigh 33 deaths certain, against two contingent on the invasion of an epidemic Small Pox, and then we have to consider, whether there might not be nearly as great a chance of two persons out of 10,000 inoculated for Small Pox, taking a fatal Small Pox on exposure, at a subsequent period of life, to a virulent contagion.” I shall conclude the evidence I think it necessary to bring forward on this part of my subject with the following extract from the Report of the National Vaccine Establishment for 1820. In reference to the occasional cases wherein the protection from Vaccination is not quite complete, the Board observes,—“Yet the value of this important resource is not disparaged in our judgment; for after all, these cases bear a very small proportion to the number of those who are effectually protected by it. The reports of the Vaccinators at the several stations in the metropolis, give only eight cases of Small Pox out of nearly 67,000 vaccinated by them, since the first establishment of this board; and as the Small Pox has prevailed extensively in London, these persons so vaccinated, must have been frequently exposed to contagion, and consequently the protecting effect of Vaccination must have been submitted to as severe a test as can well be imagined. Moreover, we have the most undoubted proofs from experience, that where Vaccination has been performed perfectly, Small Pox, occurring after it, is almost universally a safe disease; and though ushered in by severe symptoms, has hardly ever failed to be cut short before it had reached that period at which it becomes dangerous to life.”
I shall not weaken the force of this evidence by entering into any minor question connected with this great subject—such as the probability of many of those, in whom Small Pox has succeeded to Vaccination, having passed through the latter process imperfectly, either in consequence of the matter employed not having been genuine; of the constitution not having shown adequate signs of being properly influenced by the process; or of the latter having been interfered with in its progress, by the accidental injury of the pustules, &c. No doubt all these causes may have had some effect, in consequence of the carelessness of parents, or of the practice of non-professional inoculators: in a matter of so much importance then, it behoves parents to guard against these causes of failure, which it is now certainly within the power of the poorest to do. Nor shall I detail the arguments by which Professor Thomson has rendered it probable that the pustular eruption, which has been so long known in this country under the name of Chicken Pox, is very nearly related to Small Pox itself, and is in reality the effect of the same infectious virus modified by various incidental circumstances; such as season of the year, the previous existence of Small Pox or of Cow Pox in those affected by it, or some peculiarity in their constitution not sufficiently obvious to be recognised by our senses. When I rest my proof of the power of Vaccination over the destructive consequences of Small Pox on the results which have been detailed, I am satisfied that it is fixed upon a basis too firm to be shaken by argument, and which will long outlive the feeble attacks of ignorance or prejudice.
CONCLUSION.
The following are the important conclusions which may obviously be deduced from the satisfactory evidence which has been detailed.
1. That Vaccination has, within the space of twenty-five years, been the direct means of preserving, within the London[[8]] Bills of Mortality alone, a number of lives amounting to 21,127; and that if we extend the ratio of calculation to the whole of Great Britain and Ireland, it will appear that not fewer than 393,356 lives have been saved by this most valuable discovery, while an equal number have been preserved from “blindness, deformity, scrofula, or broken constitutions.”