London Mortality and Small-Pox
The [first] and largest of the diagrams illustrating this question is that exhibiting the mortality of London from the year 1760 down to the present day (see end of volume). It is divided into two portions, that from 1750 to 1834 being derived from the old “Bills of Mortality,” that from 1838 to 1896 from the Reports of the Registrar-General.
The “Bills of Mortality” are the only material available for the first period, and they are far inferior in accuracy to the modern registration, but they are probably of a fairly uniform character throughout, and may therefore be as useful for purposes of comparison as if they were more minutely accurate. It is admitted that they did not include the whole of the deaths, and the death-rates calculated from the estimated population will therefore be too low as compared with those of the Registrar-General, but the course of each death rate—its various risings or fallings—will probably be nearly true.[7] The years are given along the bottom of the diagram, and the deaths per million living are indicated at the two ends and in the centre, the last four years of the Bills of Mortality being omitted because they are considered to be especially inaccurate. The upper line gives the total death-rate from all causes, the middle line the death-rate from the chief zymotic diseases—measles, scarlet-fever, diphtheria, whooping-cough and, fevers generally, excluding small-pox, and the lower line small-pox only. The same diseases, as nearly as they can be identified in the Bills of Mortality according to Dr. Creighton, are given in the earlier portion of the diagram from the figures given in his great work, A History of Epidemics in Britain. With the exception of these zymotics the diagram is the same as that presented to the Royal Commission (3rd Report, diagram J.), but it is carried back to an earlier date.
Let us now examine the lowest line, showing the small-pox death-rate. First taking the period from 1760 to 1800, we see, amid great fluctuations and some exceptional epidemics, a well-marked steady decline which, though obscured by its great irregularity, amounts to a difference of 1,000 per million living. This decline continues, perhaps somewhat more rapidly, to 1820. From that date to 1834 the decline is much less, and is hardly perceptible. The period of Registration opens with the great epidemic of 1838, and thenceforward to 1885 the decline is very slow indeed; while, if we average the great epidemic of 1871 with the preceding ten years, we shall not be able to discover any decline at all. From 1886, however, there is a rather sudden decline to a very low death-rate, which has continued to the present time. Now it is alleged by advocates of vaccination, and by the Commissioners in their Report, that the decline from 1800 onwards is due to vaccination, either wholly or in great part, and that “the marked decline of small-pox in the first quarter of the present century affords substantial evidence in favour of the protective influence of vaccination.”[8] This conclusion is not only entirely unwarranted by the evidence on any accepted methods of scientific reasoning, but it is disproved by several important facts. In the first place the decline in the first quarter of the century is a clear continuation of a decline which had been going on during the preceding forty years, and whatever causes produced that earlier decline may very well have produced the continuation of it. Again, in the first quarter of the century, vaccination was comparatively small in amount and imperfectly performed. Since 1854 it has been compulsory and almost universal; yet from 1854 to 1884 there is almost no decline of small-pox perceptible, and the severest epidemic of the century occurred in the midst of that period. Yet again, the one clearly marked decline of small-pox has been in the ten years from 1886 to 1896, and it is precisely in this period that there has been a great falling off in vaccination in London from only 7 per cent. less than the births in 1885 to 20·6 per cent. less in 1894, the last year given in the Reports of the Local Government Board; and the decrease of vaccinations has continued since. But even more important, as showing that vaccination has had nothing whatever to do with the decrease of small-pox, is the very close general parallelism of the line showing the other zymotic diseases, the diminution of which it is admitted has been caused by improved hygienic conditions. The decline of this group of diseases in the first quarter of this century, though somewhat less regular, is quite as well marked as in the case of small-pox, as is also its decline in the last forty years of the 18th century, strongly suggesting that both declines are due to common causes. Let any one examine this diagram carefully and say if it is credible that from 1760 to 1800 both declines are due to some improved conditions of hygiene and sanitation, but that after 1800, while the zymotics have continued to decline from the same class of causes one zymotic—small-pox—must have been influenced by a new cause—vaccination, to produce its corresponding decline. Yet this is the astounding claim made by the Royal Commissioners! And if we turn to the other half of the diagram showing the period of registration, the difficulty becomes even greater. We first have a period from 1838 to 1870, in which the zymotics actually rose; and from 1838 to 1871, averaging the great epidemic with the preceding ten years, we find that small-pox also rose, or at the best remained quite stationary. From 1871 to 1875 zymotics are much lower, but run quite parallel with small-pox; then there is a slight decline in both, and zymotics and small-pox remain lower in the last ten years than they have ever been before, although in this last period vaccination has greatly diminished.
Turning to the upper line, showing the death-rate from all causes, we again find a parallelism throughout, indicating improved general conditions acting upon all diseases. The decline of the total death-rate from 1760 to 1810 is remarkably great, and it continues at a somewhat less rate to 1830, just as do the zymotics and small-pox. Then commences a period from 1840 to 1870 of hardly perceptible decline partly due to successive epidemics of cholera, again running parallel with the course of the zymotics and of small-pox, followed by a great decline to the present time, corresponding in amount to that at the beginning of the century.
The Commissioners repeatedly call attention to the fact that the mortality from measles has not at all declined and that other zymotics have not declined in the same proportion as small-pox, and they argue: “If improved sanitary conditions were the cause of small-pox becoming less, we should expect to see that they had exercised a similar influence over almost all other diseases. Why should they not produce the same effect in the case of measles, scarlet fever, whooping-cough, and indeed any disease spread by contagion or infection and from which recovery was possible?” This seems a most extraordinary position to be taken in view of the well-known disappearance of various diseases at different epochs. Why did leprosy almost disappear from England at so early a period and plague later on? Surely to some improved conditions of health. The Commissioners do not, and we may presume cannot, tell us why measles, of all the zymotic diseases, has rather increased than diminished during the whole of this century. Many students of epidemics hold that certain diseases are liable to replace each other, as suggested by Dr. Watt, of Glasgow, in the case of measles and small-pox. Dr. Farr, the great medical statistician, adopted this view. In his Annual Report to the Registrar-General in 1872 (p. 224), he says: “The zymotic diseases replace each other; and when one is rooted out it is apt to be replaced by others which ravage the human race indifferently whenever the conditions of healthy life are wanting. They have this property in common with weeds and other forms of life: as one species recedes another advances.” This last remark is very suggestive in view of the modern germ-theory of these diseases. This substitution theory is adopted by Dr. Creighton, who in his History of Epidemics in England suggests that plague was replaced by typhus fever and small-pox; and, later on, measles, which was insignificant before the middle of the seventeenth century, began to replace the latter disease. In order to show the actual state of the mortality from these diseases during the epoch of registration, I have prepared a [diagram (II.)] giving the death-rates for London of five of the chief zymotics, from the returns of the Registrar-General, under the headings he adopted down to 1868—for to divide fevers into three kinds for half the period, and to separate scarlatina and diphtheria, as first done in 1859, would prevent any useful comparison from being made.
The lowest line, as in the larger diagram, shows Small-pox. Above it is Measles, which keeps on the whole a very level course, showing, however, the high middle period of the zymotics and two low periods, from 1869 to 1876, and from 1848 to 1856, the first nearly corresponding to the very high small-pox death-rate from 1870 to 1881; and the other just following the two small-pox epidemics of 1844 and 1848, thus supporting the view that it is in process of replacing that disease. Scarlatina and diphtheria show the high rate of zymotics generally from 1848 to 1870, with a large though irregular decline subsequently. Whooping-cough shows a nearly level course to 1882 and then a well-marked decline. Fevers (typhus, enteric, and simple) show the usual high middle period, but with an earlier and more continuous decline than any of the other zymotic diseases. We thus see that all these diseases exhibit common features though in very different degrees, all indicating the action of general causes, some of which it is by no means difficult to point out.
In 1845 began the great development of our railway system, and with it the rapid growth of London, from a population of two millions in 1844 to one of four millions in 1884. This rapid growth of population was at first accompanied with overcrowding, and as no adequate measures of sanitation were then provided the conditions were prepared for that, increase of zymotic disease which constitutes so remarkable a feature of the London death-rates between 1848 and 1866. But at the latter date commenced a considerable decline both in the total mortality and in that from all the zymotic diseases, except measles and small-pox, but more especially in fevers and diphtheria, and this decrease is equally well explained by the completion, in 1865, of that gigantic work, the main drainage of London. The last marked decline in small-pox, in fevers, and to a less marked degree in whooping-cough, is coincident with a recognition of the fact that hospitals are themselves often centres of contagion, and the establishment of floating hospitals for London cases of small-pox. Perhaps even more beneficial was the modern system of excluding sewer-gas from houses.
We thus see that the increase or decrease of the chief zymotic diseases in London during the period of registration, is clearly connected with adverse or favourable hygienic conditions of a definite kind. During the greater part of this period small-pox and measles alone showed no marked increase or decrease, indicating that the special measures affecting them had not been put in practice, till ten years back the adoption of an effective system of isolation in the case of small-pox has been followed by such marked results wherever it has been adopted as to show that this is the one method yet tried that has produced any large and unmistakable effect, thus confirming the experience of the town of Leicester, which will be referred to later on.
The Commissioners in their Final Report lay the greatest stress on the decline of small-pox at the beginning of the century, which “followed upon the introduction of vaccination,” both in England, in Western Europe, and in the United States. They declare that “there is no proof that sanitary improvements were the main cause of the decline of small-pox,” and that “no evidence is forthcoming to show that during the first quarter of the nineteenth century these improvements differentiated that quarter from the last quarter or half of the preceding century in any way at all comparable to the extent of the differentiation in respect to small-pox” (p. 19 par. 79). To the accuracy of these statements I demur in the strongest manner. There is proof that sanitary improvements were the main cause of this decline of small-pox early in the century, viz., that the other zymotic diseases as a whole showed a simultaneous decline to a nearly equal amount, while the general death-rate showed a decline to a much greater amount, both admittedly due to improved hygienic conditions, since there is no other known cause of the diminution of disease; and that the Commissioners altogether ignore these two facts affords, to my mind, a convincing proof of their incapacity to deal with this great statistical question. And, as to the second point, I maintain that there is ample direct evidence, for those who look for it, of great improvements in the hygienic conditions of London quite adequate to account for the great decline in the general mortality, and therefore equally adequate to account for the lesser declines in zymotic diseases and in small-pox, both of which began in the last century, and only became somewhat intensified in the first quarter of the present century, to be followed twenty years later by a complete check or even a partial rise. This rise was equally marked in small-pox as in the other diseases, and thus proved, as clearly as anything can be proved, that its decline and fluctuations are in no way dependent on vaccination, but are due to causes of the very same general nature as in the case of other diseases.
To give the evidence for this improvement in London hygiene would, however, break the continuity of the discussion as to small-pox and vaccination; but the comparison of the general and zymotic death-rates with that of small-pox exhibits so clearly the identity of the causes which have acted upon them all as to render the detailed examination of the various improved conditions that led to the diminished mortality unnecessary. The diagram showing the death-rates from these three causes of itself furnishes a complete refutation of the Commissioners’ argument. The evidence as to the nature of the improved conditions will be given in another work to be published shortly.