Vaccination (Latin vacca="a cow"). Towards the end of the last century Edward Jenner, a surgeon practising in Gloucestershire, was led to make inquiry into the truth of a notion to which his attention was directed, to the effect that milkers and others who had suffered from cowpox were incapable of contracting smallpox (variola). Jenner instituted a number of experiments, and published the results in 1798 in his work entitled An Inquiry into the Causes and Effects of the Variole Vaccinae. In each of the two following years he published further papers on the subject, which was taken up by other observers, and speedily assumed considerable prominence. Jenner held that material taken from cases in which a certain eruption was found affecting the teats and udders of cows possessed the power, when inoculated into the human subject, of protecting from smallpox. The particular cow-disease in question he called variolae vaccinae; hence the title of his first paper, and hence the application of the term vaccination to this method of preventing an attack of smallpox. The efficacy of vaccination was tested by numerous inquirers, who satisfied themselves that a person who had been submitted to the operation acquired protection against an attack of smallpox, as tested by a subsequent inoculation with smallpox matter; and vaccination during the early part of the present century gradually superseded the method of smallpox inoculation which had hitherto been largely adopted with a view to preventing a severe attack of variola. Vaccination was taken up abroad, and in this country it obtained so much favour that it was enacted in 1838 that it should be provided gratuitously, and in 1854 it was made compulsory. In 1871 an Act was passed providing for the systematic enforcement of vaccination, and for the appointment of paid vaccination officers. On the other hand, the old operation of variolous inoculation, which had gradually fallen into disuse, was in 1840 made illegal on account of the risk of the communication of infection, from those who had been submitted to the operation, to unprotected persons. With the disuse of variolous inoculation the possibility of applying the test employed by the early observers, of insusceptibilityto variolous inoculation subsequent to a successful vaccination, no longer existed. A mass of statistical evidence, was, however, becoming accumulated, showing the effect of vaccination upon the incidence of smallpox. While, however, this evidence clearly showed the importance of vaccination as a means of protection, it was found such protection does not last for an indefinite period, and the desirability of repeating the operation after the lapse of a term of years became manifest. It was, moreover, ascertained that in cases where smallpox attacked persons who had been vaccinated, but the protective influence of whose vaccination was not sufficient to altogether prevent the manifestation of the disease, the severity of the malady was in direct relation with the number, extent, and character of the vaccination marks. The importance of revaccination and of the proper performance of the operation of vaccination thus became recognized. Between 1889 and 1897 vaccination was made the subject of exhaustive inquiry by a Royal Commission. During recent years there has been, particularly in London, a marked increase in vaccination default. On the other hand, however, the removal of smallpox hospitals from crowded localities has had marked influence in limiting the spread of the disease; this has been especially notable in London since 1885, in correspondence with the adoption of the system of isolating cases of smallpox in the hospital ships in Long Reach, near Dartford, in Kent. In 1898 an Act was passed effecting great changes in the law, mainly relating to the substitution of domiciliary vaccination for vaccination at public stations, the use of glycerinated calf lymph in all cases where required, the extension of the period within which a parent or guardian is required to cause a child to be vaccinated from three to six months from the birth of the child, and the exemption from penalties of conscientious objectors. It is hoped that as a result of the working of this Act vaccination default will diminish. A system for further facilitating revaccination is still, however, much needed in this country.
Until within recent years vaccination was almost exclusively practiced by arm-to-arm inoculations, lymph taken from the vesicles of one subject (usually on the eighth day) being inoculated into another subject; but the practice of inoculating directly from the calf has of late years been adopted in France, Germany, and the United States, and since 1881 the English Government has had at work an animal vaccine station in London. At this establishment in Lamb's Conduit Street a large number of vaccinations directly from the calf are now performed, and in Prussia calf lymph is said to be exclusively used. The phenomena of a successful vaccination in a healthy infant are as follows: -- At the site of the insertion a small elevation develops on the second or third day. On the fifth or sixth day this papule has become a vesicle, and presents a slight central depression. The vesicle attains maturity on the eighth day, when it is full of clear lymph, and is surrounded by a circular inflamed area which extends until its diameter is from one to three inches. About the tenth day the inflammation begins to pass away, the fluid of the vesicle, which has now become opaque, begins to dry up, and a scab is formed which separates, leaving a scar, at the end of about three weeks.
The altered age incidence of smallpox in correspondence with the increasing adoption of vaccination is a phenomenon which strongly corroborates the evidence, in which it has not been found possible, by those who do not believe in the efficacy of vaccination, to explain away. In the supplement to the 14th Annual Report to the Local Government Board the following statement is made by Sir George Buchanan, then Medical Officer of the Board: -- "The Register-General divides the period 1847 to 1880 (during which the causes of death were abstracted in combination with ages) into proportions -- a first, namely, of six years (1847-53), when vaccination was optional; a second of eighteen years (1854-71), when it was obligatory, but not efficiently enforced; and a third of nine years (1872-80), when it was obligatory and more efficiently enforced by vaccination officers. For England and Wales the mean annual death-rate from smallpox of children under five years old in these several periods fell from 1,617 per million, at which it stood during the period of optional vaccination, first to 817 and then to 323; and the death-rate of children between five and ten years fell in a similar way from 337 to 243 and then to 186. The rates for children between ten and fifteen years in the three successive periods of time have remained without much change, having been 94, 88, 98. At higher ages of life, to which I shall immediately recur, there has not been decrease, but increase, in the rate of death by smallpox. Nevertheless, when all ages are considered together, the average annual death-rate by smallpox, 305 million persons living, during the period of optional vaccination, is found to have fallen to 223 during the following period of obligatory vaccination, and during the period of enforced vaccination to 156."
This alteration in the age incidence of smallpox is readily explicable when it is realized that the resistance to smallpox in adult life, which was afforded in pre-vaccination times by an attack of the disease in infancy, was practically complete, while it has been exchanged nowadays for the resistance furnished by vaccination, which has served to protect more especially the persons upon whom the operation has been comparatively recently performed, and has not extended the same degree of immunity to those in whom the effects of the operation have had time to become weakened. Thus, while in pre-vaccination times the preponderating evidence of the disease was upon childhood, among the vaccinated childhood is practically exempt, and smallpox is only fatal in later years when the protective influence of the operation has become diminished. The remarkable fact remains to be noted that among unvaccinated persons the original preferential incidents of the malady upon the earlier ages has continued to manifest itself. The other lines of argument which all point to the same conclusion may be briefly referred to. The effects of revaccination have now become abundantly evident, and it is clear that communities in which revaccination is carried out employed even greater immunity from the disease than those in which an original vaccination in infancy alone obtains. Prussia, in which revaccination was made compulsory in 1874, the British Army and Navy, and the case of attendants in smallpox hospitals, are instances in point. There are, again, the elaborate statistical results of Mr. Marson and Dr. Gayton, which shows the influence exerted by the character and extent of the operation; the mortality from smallpox varying in close correspondence with the thoroughness with which the operation, designed to afford protection, has been performed. An outbreak of smallpox in Sheffield in 1887-88 was made the subject of an elaborate report by Dr. Barry, and that the important evidence as to the value of vaccination afforded by the facts which he collected may be studied by those interested in the subject either in his original report or in the introduction to and summary of the report which is printed in the 18th Annual Report of the Local Government Board. Much has been written concerning the alleged risks of vaccination, but exhaustive inquiry has shown that when the operation is performed with proper care the risk is infinitesimal, and that it in no way admits to being weighed in the balance against the benefit which is conferred.