VACCINATION, (from vacca, a cow), is the artificial production of a disease, originally obtained from the cow, (cow-pox), by bringing the matter of that disease in contact with the living fibre.

To Dr. Edward Jenner we are indebted for the discovery of vaccination. His attention was first directed to the subject by the popular belief which existed in Gloucestershire, where he resided, that those who were infected with matter from the sores on the udder of the cow, were ever after secured from the contagion of small-pox. It was not, however, till the 14th of May 1796, that he made it the subject of direct experiment, by taking matter from the sore on the hand of a dairymaid who had contracted cowpox from the udders of her master’s cows, and applying it, by means of two superficial incisions, to the arm of a boy. Pustules somewhat similar to those of small-pox, but darker in their hue, and filled with a limpid fluid, were produced, and became surrounded with an erysipelatous or red circle, but the whole died away, leaving on the inoculated part scabs and subsequent eschars, without producing any other inconvenience. On the seventh day after the operation, the boy complained of some uneasiness in the arm-pit; on the ninth he became chilly, had headach, loss of appetite, and was otherwise indisposed, and passed a restless night, but was well by next day. As the object of the experiment was to ascertain whether the cow-pox gave immunity from the small-pox, he was on the 1st of July inoculated with smallpox matter, but no disease was produced; and the same result was obtained when this was repeated some months afterwards. Numerous experiments of the same kind were afterwards made; and they ended in establishing the fact that the matter of cow-pox protected the human body from being acted on by the infection of small-pox, while it was itself a mild and safe disease, exciting little more constitutional disturbance than what resulted from the local sore.

Dr. Jenner accounted for this singular fact, by asserting that cow-pox was nothing else than small-pox modified, or deprived of all its noxious qualities, by having passed through the system of the cow; and that the disease in the heel of the horse, called grease, which he showed was capable of producing the vaccine vesicle in the cow, was also but a variety of the same disease. In fact, he at first regarded both small-pox and cow-pox as originally derived from the horse.

The publication of such an interesting fact did not fail to excite general attention; and, accordingly, the very same year in which Dr. Jenner’s Inquiry made its appearance, Dr. Pearson published the results of his investigations, which tended to confirm the opinion advanced by Dr. Jenner as to the anti-variolous powers of the cow-pox. In two points alone did he dissent. He regarded cow-pox and small-pox as two very different diseases, and denied that the cow-pox could be produced by the matter of the diseased heel of the horse; and he was supported in his opinion by the inquiries of Sir Isaac Pennington, the arguments of Dr. Parr, and the experiments of Dr. Woodville, and of Mr. Simmons.

Other experimentalists were, however, much more successful in confirming the opinion of Dr. Jenner as to the analogy or rather identity of the disease of the horse’s heel and the cow-pox. Mr. Tanner succeeded in communicating the cow-pox to the cow, by inserting on the udder some liquid matter taken from the diseased heel of the horse; and the experiments of Mr. Lupton and Dr. John Loy corroborated the same fact. Dr. Loy, indeed, found that even the equine matter produced in man as perfect vaccine vesicles, as that derived from the cow itself, and afforded equal protection from the infection of small-pox. These conclusions have been confirmed by subsequent experimentalists both in this country and on the continent, so that it is now to be regarded as an established fact, that grease and cow-pox are the same complaint, modified by the constitution of the animals in which they occur.

Dr. Woodville of the London Small-Pox Hospital lent his aid to ascertain, by direct experiment on a large scale, whether the introduction of the mild disease, cow-pox, was worthy of the encomiums bestowed upon it by Dr. Jenner and Dr. Pearson, and whether it really guarded the system from a subsequent attack of that loathsome and fatal disease, the small-pox. The results of these experiments were published in 1799, by which time he had vaccinated six hundred individuals. In most of these cases, small-pox inoculation had been performed at a subsequent period, to test the efficacy of the protective power of the cow-pox, but not one of them took the small-pox. An anomalous occurrence, however, showed itself in nearly three-fifths of the patients vaccinated at the Small-Pox Hospital. Pustular eruptions, more or less numerous, resembling those of small-pox, appeared on various parts of the body, in some cases maturating much in the same way as the pustules do in that disease, in others fading away without proceeding to the formation of matter. Dr. Jenner, at the time when the circumstance occurred, endeavoured to explain it, by supposing that it was owing to some peculiarity in the air which these patients breathed, or to a contamination of the original cow-pox matter with smallpox. That it could not be owing to contamination with small-pox matter, Dr. Woodville showed from the fact, that the same matter, when employed for the vaccination of individuals out of the Small-Pox Hospital, did not produce these same pustular eruptions; and some of the identical matter sent to the country, and used in vaccinating one thousand individuals, only produced pustular eruptions in two cases. Dr. Woodville, therefore, very justly drew the inference, that the cases vaccinated at the Small-Pox Hospital differed from those vaccinated elsewhere, in being placed in the centre of a variolated atmosphere, to the action of which the pustular eruption was to be ascribed; a statement which was in a manner proved at the time by the fact, that though at first nearly three-fifths of all the cases vaccinated showed pustular eruptions, yet the eruptions afterwards diminished so much, that of the last hundred cases which be published in his first Reports, only seven were thus affected [7:21:535]Subsequent observation has shown that this was in reality the true explanation of the fact.

Dr. Woodville considered small-pox and cow-pox as very closely allied in their nature, indeed, “to a very principal point essentially the same,” and consequently recommended the general adoption of cow-pox, as an effectual preservative from the infection of small-pox, as perfectly sale and free from danger, and incapable of being propagated by infectious effluvia. This last he considered a very strong circumstance in its favour, since small-pox, even in its mildest form, as produced by inoculation, tended greatly to swell the bills of mortality, by spreading the infection from the sick to the healthy.

It was during the progress of Dr. Woodville’s experiments at the Small-Pox Hospital that the merits of vaccination began to be appreciated, and the practice of it generally introduced into all parts of this country; and the publication of his Observations in 1800 may be regarded as marking this epoch. At this period, indeed, the efficacy of vaccination as an anti-variolous agent was so generally admitted, and the practice so universally adopted, that, in the course of a few months. Its benefits were extended to many thousand persons in all parts of this island, and matter found its way to France. Italy, Germany, Holland, Turkey, most of our colonies, and the United States of North America. Numerous were the publications, in all languages, announcing the success of the practice; and almost every one agreed in this, that it gave as perfect protection from the infection of small-pox, as if the individual had once had the natural or inoculated disease.

Many of the partizans of vaccination, however, went much farther than this, and asserted that those who had once gone through the vaccine disease, were at no subsequent period of their lives liable to take small-pox. When, therefore, cases of small-pox did occur after vaccination, they endeavoured to explain away the fact, by asserting that it was not true small-pox, or that the individual had not gone through the true, but a spurious vaccine disease. This was, indeed, claiming for vaccination a power which was not possessed by any other disease. There is a class of diseases which usually occur but once during the course of life, but though a second attack is not a common occurrence, still it is every now and then met with; and there are very few medical men of any standing in their profession who have not met with cases of second attacks of measles, scarlet fever, small-pox, typhus, &c. Dr. Thomson of Edinburgh, in his work on the Varioloid Epidemic of 1818, was the first to point out this clearly with regard to small-pox; and had the circumstance been duly attended to when vaccination was first introduced. It would have prevented much of the controversy which has since arisen. It was unreasonable to expect from vaccination a protective power greater than that afforded by small-pox itself; and yet it was from the advocates of vaccination advancing this doctrine, —a doctrine apparently borne out by the perfect immunity afforded to so many thousands vaccinated in all parts of Europe on its finit introduction,—that others, who had seen cases of small-pox after it, were led to deny altogether its anti-variolous power, or at least to affirm that it only gave immunity from the disease for a very limited number of years.

It was not, however, till the year 1818, that the true value of the protective powers of vaccination was properly understood. During the years 1816-17-18, small-pox raged epidemically in various parts of Europe, and attacked both the vaccinated and variolated, as well as those who had neither had cow-pox nor small-pox. Chicken-pox was at the same time extremely prevalent, and the phenomena of the two diseases were found to be frequently and generally interchanged. Dr. Hodenpyl of Rotterdam, Dr. Thomson of Edinburgh, and MM. Berard and De Lavit of Montpellier, who all described this epidemic, agreed in regarding small-pox and chicken-pox as the same disease, which could be shown to originate from the same source. But the most important fact, and the one most interesting to humanity, was the ascertaining the comparative mortality of small-pox, when it attacked these three classes :—1st, the vaccinated; 2d, the variolated, i.e. those who had small-pox; and, 3d, those who had neither been vaccinated nor had small-pox. The conclusions at which these different writers arrived were nearly the same. Of those who had neither had cow-pox nor small-pox, 1 out of every 4 who were seized with the disease died; of those who had small-pox naturally, or by inoculation, 1 out of every 25 to 1 in 75 died; while of those who had been vaccinated, and were afterwards seized with small-pox, not more than 1 in 330 cases died: thus showing the great superiority of vaccination even to the small-pox itself, in protecting the system from the fatal effects of a second attack. Nor is it difficult to understand how this should happen. Small-pox is a disease not only very fatal, as proved by its cutting off a fourth of all whom it attacks, but it disfigures or renders infirm from an eighth to a tenth of those who recover. Its action is besides found to develope any latent disease, but particularly any scrofulous tendency which may exist in the constitution, and is thus indirectly the cause of death to a much larger portion of the human race than what at first sight appears. It is not therefore to be wondered at, that small-pox, attacking for the second time a constitution thus enfeebled, should cause a much greater proportion of deaths than takes place when it occurs after vaccinal ion; for no fact is more firmly established than this, that vaccination neither develops any latent malady, nor engenders a predisposition to any particular disease.

The fact above mentioned, of the comparative mortality of the three classes, viz. the vaccinated, the variolated, and the non-vaccinated, has been, since 1818, repeatedly demonstrated. One of the most accurate and interesting details, and one which ought to set the point for ever at rest, is that given by M. Bousquet in his Traité de la Vaccine, as having occurred at Marseille during the epidemic small-pox of 1825. The population of Marseille, amounting to 40,000, may be divided into three classes, of which the respective numbers stand thus: 30,000 vaccinated; 8000 neither vaccinated nor variolated; and 2000 variolated, that is, who had the smallpox either naturally or by inoculation. Of the 30,000 vaccinated, about 2000 were seized with the prevalent smallpox epidemic, of which number twenty died, or one for every hundred affected. Of the 2000 variolated, twenty were attacked, and four died, or one in every five cases. Of the 8000 non-vaccinated, 4000 were affected, and of this number 1000 died, or one out of every four cases. From this it follows, that one-half of the non-vaccinated, 1—15th of the vaccinated, and only l-100th of the variolated, took the disease. But such was the difference in the comparative severity of the attack in the vaccinated and variolated, that while the variolated part of the population were cut off in the proportion of one out of every 500, the vaccinated part of the population only lost one out of every 1500; or, in other words, of an equal number of variolated and vaccinated cases, three variolated died from the second attack, for every one who died of the disease after vaccination.

Many similar instances might be quoted; all of them demonstrating the very great security to the individual, and the saving of life to the community, afforded by the introduction of vaccination. This is a subject, indeed, which has engaged the attention of political economists; and as it has been calculated that in Britain alone, before the introduction of vaccination, no fewer than 35,000 were annually cut off by small-pox, while in France the deaths from that cause amounted to 85,685, and proportionally large numbers occurred in other parts of Europe and America, the saving [7:21:536]of life effected by this invaluable discovery must be immense.

Though the benefits of vaccination were thus clearly proved, the public confidence in it has been attempted to be shaken by raising the outcry, that the vaccine virus, if it really possesses anti-variolous powers, loses them as life advances; so that, at the end of a few years, those vaccinated individuals are as liable to the attack of small-pox as if they had never been affected by the disease. It is fortunately an easy matter to trace such an opinion to its true sources; namely, to a disbelief in the fact, that small-pox can occur twice in the same individual; and to a disbelief in the identity of small-pox and cow-pox. Those holding such opinions as these, see every thing through the mist of prejudice, and represent every instance of the occurrence of small-pox after vaccination as an additional proof of the correctness of their theory; shutting their eyes to the facts daily happening around them, that a second attack of small-pox is not only by no means a very rare occurrence, but that it is a much more dangerous and fatal disease than small-pox after vaccination, cutting off at least three times as many victims.

As the first of these objections has. It is conceived, been satisfactorily shown to rest on no solid grounds, we are next to examine whether the second stands on any better foundation.

Every writer who has opposed vaccination, whatever may have been his other grounds of objection, has constantly set out with the proposition, that there are certain diseases which occur but once in the course of life, and which effect some unknown change on the constitution, rendering it unsusceptible of a second attack of the same disease. As they regard smallpox and cow-pox as two distinct diseases, they cannot imagine how the one disease should guard the human frame from the ravages of the other; and one of the latest writers on the subject of vaccination, Dr. G. Gregory of the Small-Pox Hospital, London, actually declares, that “vaccination is not small-pox, but just the reverse—the antagonist principle.” In order to answer such an objection, all that is requisite is, to show that small-pox and cow-pox are really identical, the latter only modified by having passed through the system of the cow, as originally advanced by Dr. Jenner, the father of vaccination.

It was announced so early as 1802, by Professor Viborg of Copenhagen, that, at Berlin, small-pox was communicated to the cow by inoculation; but the details of these experiments do not appear to have reached this country, and all attempts to repeat them here have failed. It was not till 1830, that any detailed account of successful experiments of this kind were published, when Dr. Sonderland of Barmen announced that he could produce the true vaccine disease in the cow at pleasure, by covering the animal with the blankets from the bed of a patient who had died of smallpox, and by hanging them up around it, that it might breathe the effluvia arising from them. In a few days, he says, the animal became sick, and pustules appeared on the udder and other parts, precisely similar to the cow-pox vesicles, and filled, like them, with lymph. This lymph, transferred to the human subject, he found to produce the genuine vaccine vesicle, together with the usual constitutional disturbance, and to protect the individual from the small-pox virus or contagion. In fact, such a change was effected on the small-pox matter, during its transit through the system of the cow, that it was converted from a virulent and fatal into a mild and safe disease.

The announcement of this curious experiment incited others to repeat it, though without success; and it was not till 1839 that Mr. Robert Ceely, surgeon to the Buckinghamshire Infirmary, succeeded in proving the identity of the two diseases, by communicating small-pox by inoculation to the cow, and finding it produce the true cow-pox disease. He however failed to communicate small-pox to the cow after the manner found successful by Dr. Sonderland. Mr. Ceely inoculated heifers with the matter of smallpox, and found it to produce genuine vaccine vesicles, which ran their course like the natural or inoculated cow-pox, and furnished limpid lymph for vaccination. The lymph was employed in vaccinating many children, and differed in no respects from that obtained from the natural cow-pox vesicle of the cow. It ran the same course when introduced by punctures on the arm; did not give rise to any eruption on the skin, any more than primary vaccine lymph; and afforded equal protection against small-pox, as found by exposing the children to the small-pox effluvium, and also by inoculating them with small-pox virus; in fact. It did not in any respect differ from ordinary vaccine lymph, as obtained from the natural vaccine vesicle.

Nothing could be more satisfactory than the result of such an experiment. For here it is proved, beyond the possibility of a doubt, that small-pox and cow-pox are but varieties of the same disease. It is therefore no longer to be regarded as an anomaly, that cow-pox should protect the system from an attack of small-pox, but it is in beautiful accordance with what has been generally admitted to be a law in nature, that certain diseases, once undergone, protect the system from a subsequent attack.

The chief objection to vaccination having been. It is hoped, answered satisfactorily. It only remains to show, that the protective powers of vaccination do not wear out of the system as life advances, any more than those of small-pox itself. This is a most important inquiry; as nothing is more likely to prove hurtful to the cause of vaccination, and render the public careless of securing to themselves its benefits, than the belief, that they would require to submit to revaccination every ten or fifteen years, and that at no period of their lives they could with certainty reckon on escaping the small-pox.

Starting from the point which has been proved, that the cow-pox and the small-pox are the same disease, all analogy shows that the system having once passed through this disease, is not in general susceptible of a second attack. More than forty years have now elapsed since vaccination was introduced; and if, as the opponents of vaccination assert. Its anti-variolous powers wore out of the system in a few years, why does it happen that small-pox is not now as deadly a scourge among the grown population, as it was before the introduction of vaccination? It has not been for want of epidemics of small-pox that the grown population has escaped for so many years. At Marseille, after a lapse of twenty-five years. It was found that the protective powers were not in the least diminished. Of the 30,000 who had undergone vaccination in that city, only twenty fell victims to the small-pox, or one out of every 1500 individuals: while of the 8000 who had not been vaccinated, no fewer than 1000 died, or one out of every eight persons. Here was no falling off of the protective power of vaccination after twenty-five years. Nay, the security afforded by vaccination was even greater than that of small-pox itself, for out of a population of 2000 who had had small-pox, no fewer than four died, or one out of every 500 individuals; exactly three times as many as those who had been protected by vaccination. But this is only one of many similar instances which might be produced.

It having been found, that from a sixth to a third of those who have been vaccinated are capable of receiving vaccination a second time, after the lapse of a greater or lesser number of months or years, the opponents of vaccination adduce this as an additional argument to prove that its anti-variolous powers wear out of the system. But such assertions will not bear a moment’s serious reflection. Allowing, for the sake of argument, that all those who could be revaccinated successfully, would be equally liable to an attack [7:21:537]of small-pox, if exposed to its influence, (which they are not, as it has been clearly proved by experiment that individuals may be successfully revaccinated, and yet be unsusceptible of the poison of small-pox,) what would be the result? Their chances of recovery would be as 100 to one, that of dying as one to 100. Or, in other words, if 100 were attacked with small-pox after vaccination, only one would die; whereas, if 100 who had formerly had smallpox were again attacked, no fewer than twenty would die. Now this is stating the facts in their most favourable light for the opponents of vaccination, as, according to what has occurred in several of the variolous epidemics, only one of the vaccinated has died out of 330 individuals attacked; but either of the statements is quite sufficient to prove the immense superiority of vaccination to inoculation, and also the fact, that the security afforded does not decrease with the advance of life.

The Royal Academy of Medicine of France, after the fullest inquiry into this subject, have arrived at the conclusion, that vaccination gives, in general, perfect protection from a subsequent attack of small-pox,—a protection fully as perfect as if the individual had gone through the smallpox itself; and when the government applied to them in 1839, to ask their advice as to whether the students at the different public schools and colleges ought to be revaccinated before leaving them, they returned for answer that they ought not, as having been once vaccinated gave protection from small-pox for the remainder of life.

It is extremely satisfactory to learn that all extended inquiries have led to the same result, that vaccination gives full protection from small-pox for life. Too little attention has, in this country, been paid to the statistics of disease, and also to vaccination, to give anything like accurate results as to the effects of vaccination in diminishing the mortality from small-pox; but in several countries of the continent of Europe, the same remissness has not been shown, and there the advantages of the general introduction of vaccination is demonstrated. One instance may suffice for illustration. In Sweden, in the year 1779, no fewer than 15,000 persons were cut off by small-pox; and in 1800, the year before the introduction of vaccination, 12,000 fell victims to the same disease. Great exertions were now made to introduce and carry into effect the beneficial practice of vaccination, when the mortality from small-pox yearly diminished, till it fell so low as eleven in the year 1822, and thirty-seven in the year 1823. Since then, “for a period of eight years, not a single case of small-pox has occurred in the dominions of his Swedish majesty: the whole inhabitants had been vaccinated.”

If the anti-variolous powers of vaccination failed after a certain number of years, say ten or fifteen, instead of having, as above stated, an annually decreasing number of smallpox cases, we should have seen them occurring in a gradually increasing ratio. But as the practice has now stood the test of a whole generation, and has been found to be as effectually protective at the end of that long period as at the beginning, we may safely acquiesce in the conclusion of the French Academy of Medicine. The truth is, that the ratio of mortality from small-pox, after vaccination, is greatly less than that of almost any disease to which the human frame is subject; and were vaccination as generally practised, and as carefully attended to, in this and other countries, as in Sweden, the sanguine hope of Jenner might yet be fulfilled, that the small-pox might be quite extinguished, (c. m.)