SMALL-POX OR VARIOLA.

The contagium of small-pox is very tenacious of life. All parts of the body, and all secretions and excretions contain it. As in typhus it adheres to every article in the room, but unlike typhus is possessed of great vitality, and if not exposed to the air may be active after many years. There is considerable evidence indicating that the contagion of small-pox may occasionally be conveyed aerially for a considerable distance, for even a quarter or half a mile from hospitals in which small-pox patients are isolated. Whether this is the aerial convection of infection, or in part at least due to carelessness of persons connected with the hospital in their movements to and fro, may remain an open question; but such hospitals in the midst of towns are in practice a mistake; and in London small-pox has been found to be more manageable since its small-pox patients were all conveyed to extra-urban hospitals. The means for the prevention of small-pox are (1) Isolation of infectious patients. (2) Disinfection of all infected articles. For particulars under these two heads, see pages 319 and 324. They must be carried out most rigidly in this disease. (3) Vaccination and re-vaccination.

Inoculation of small-pox virus was largely practised as a means of ensuring a comparatively mild attack, until it was made illegal in 1840. Sometimes, however, the attack thus produced was fatal, and every case of inoculated small-pox became a new focus of infection, and a source of high mortality, especially among young children.

Vaccination. About the year 1795 Dr. Edward Jenner was informed by a milk-maid that she could not take small-pox, as she had already contracted the natural cow-pox during milking. Many had previously heard this same statement made; but Jenner was the first to put the matter to the test. He took the lymph or virus from a woman who had accidentally acquired cow-pox (vaccinia) from a cow, and inoculated a boy with it. Some months later he inoculated the same boy with small-pox, and a second time five years afterwards, without producing small-pox on either occasion. Many other experiments were made, all confirming these results; and in 1798 Jenner published his results.

The practice of vaccination gradually became more general, and was followed by a progressive decrease in the mortality from small-pox.

Cow-pox or vaccinia is small-pox modified and mitigated by its passage through the system of the cow, and not a spontaneous disease of the cow. By its passage through the cow it has become attenuated and altered. Instead of a general eruption all over the body, there are vesicles only at the point of inoculation; and vaccinia, unlike small-pox, is not communicable from person to person except by inoculation. Furthermore it is in the vast majority of instances an extremely mild ailment, not involving more than a few days discomfort.

Objection is taken to vaccination for small-pox on the ground that serious diseases such as syphilis, erysipelas, and tuberculosis may be inoculated at the same time. With lymph obtained from healthy children this is impossible. Most of the cases of infection described have been in reality hereditary disease, the local irritation of vaccination serving to call into activity the morbid tendencies of the child. The risk of such infection is infinitesimal; it may be reduced to zero by moderate care and attention to detail. With modern antiseptic methods, it is very rare for a vaccination sore to “go wrong.” Erysipelas may be inoculated from dirt getting into a vaccination sore, as it may be into any other sore; but with cleanliness this need not occur; and in fact very seldom does occur. The risks are so small as to be negligible; and if the protection afforded is one tithe of what is claimed for it, no parent is justified in withholding this protection from his infant. The law as to vaccination requires that every infant shall be vaccinated within six months of its birth, domiciliary visits for this purpose being made by the public vaccinator. The obligation can only be avoided by a statement on oath before a magistrate by the parent of conscientious objection to vaccination.

Does Vaccination protect against Small-Pox? The registration of deaths for the whole country only began in 1837, and before this period death-rates from small-pox in terms of the population cannot be accurately stated. Since that time there has been less or more vaccination, so that it is difficult to obtain a true comparison between periods with and without vaccination. Some indication of the facts in London prior to 1801, when the first English census was taken, may be obtained from the fact that in 1796 (two years before the date of Jenner’s “Inquiry,”) small-pox reached its highest point, causing 18½ deaths out of every 100 total deaths from all causes. In the præ-vaccination period small-pox was 9 times as fatal as measles, and 7½ times as fatal as whooping-cough (McVail), while since vaccination has been practised it has sunk to an insignificant position, when compared with these diseases. Dr. Guy found that in London there were in 48 years of the seventeenth century ten epidemics, in the whole of the eighteenth century 19 epidemics, and in the nineteenth century no epidemic during which the deaths from small-pox caused one-tenth or more than one-tenth of the total deaths from all causes in any year. The worst year under obligatory vaccination in London was 1871, in which barely 4½ per cent. of the total deaths was due to small-pox, a proportion which was exceeded in the eighteenth century ninety-three times.

In Sweden, the highest death-rate before vaccination (1774-1800) was 7·23 per 1,000 inhabitants, the lowest 0·31; under permissive vaccination (1801-1815) the highest 2·57 per 1,000 inhabitants, the lowest 0·12; under compulsory vaccination (1816-85) the highest 0·94 per 1,000 inhabitants, the lowest 0·0005. It has been stated that these results, which might be extended by quotations from the statistics of other countries, have been obtained not by vaccination, but by improved sanitation, including in this term not only improved housing and better water and food supply but also increased means of isolating the infectious sick. Improved housing may by diminishing overcrowding aid in diminishing the spread of this disease. Whether in view of the immense increase in the proportion of the population which lives in towns, it can be said that this has occurred is doubtful. Hospital isolation undoubtedly prevents the spread of infection when promptly effected. But a large share of the improvement in small-pox mortality occurred before either hospital or home-isolation of small-pox patients was generally enforced. There is no reason for supposing that impure water or food, or nuisances about houses have any connection with the origin or spread of small-pox, any more than they have with the origin or spread of measles or whooping-cough; which still remain as prevalent as in the past. Further light can be thrown on the subject by an examination of the age-incidence of small-pox, and of its attack-rate and severity in vaccinated and unvaccinated respectively.

The age incidence of deaths from small-pox has, since 1847, when returns classified according to age became available, undergone a remarkable alteration. Prior to 1870 the small-pox deaths in infants nearly always formed 20 per cent. or more of the total mortality from this disease, between 1870 and 1890 they did not greatly exceed 10 per cent. of the total, while since 1890 they have again begun to form an increasing proportion of the total small-pox mortality. At ages 1-5 the change is even more remarkable. Before 1870 deaths at these ages nearly always exceeded 30 per cent. of the total; since 1870 they have varied between 5 and 14 per cent. of the total; and since 1890 they have, like the proportion of deaths under one, again increased. At the higher ages the proportion of deaths has correspondingly increased, so that the curves of age incidence have become curiously inverted.

The lowered birth-rate can only account for a small portion of this transference of the chief mortality due to small-pox from childhood to adult life.

Furthermore it must not be supposed that the only change which has occurred is that the deaths which formerly occurred in childhood now occur in adult life. The death-rate at all ages has greatly declined. The only explanation which in my judgment satisfactorily explains this remarkable change in age-incidence of small-pox mortality is the fact that vaccination protects children from small-pox and that the protection diminishes, though it never entirely disappears, with advancing years. This conclusion is confirmed by the evidence obtained as to the proportion of vaccinated and unvaccinated attacked, and as to the severity of the attacks occurring when a community is invaded by small-pox.

Attack-rate among Vaccinated.—If the protective effect of vaccination, like that of a preceding attack of small-pox, wears off, it will not be expected that no attacks of small-pox will occur among the vaccinated. For evidence of immunity from attacks we must examine the records as to revaccinated persons exposed to infection. During the six years 1890-95, out of a staff in the London small-pox hospitals varying from 64 to 320, the percentage attacked by small-pox was nil, except in 1892 when it was 1·4, and in 1893 when it was 1·9.

Taking the experience of towns in which during recent years epidemics of small-pox have occurred, the following attack-rates have occurred. By attack-rate is meant the percentage number of attacks occurring among persons living in infected houses. By fatality is meant the number dying out of 100 attacked.

ATTACK RATE UNDER 10 YEARS OF AGE.ATTACK RATE OVER 10 YEARS OF AGE.
VACCINATED.UNVACCINATED.VACCINATED.UNVACCINATED.
Dewsbury10·250·827·753·4
Leicester2·535·322·247·6
Gloucester8·846·332·250·0

Severity (Fatality) among Vaccinated.—The experience of the same three towns comes out as follows:—

FATALITY RATE UNDER 10 YEARS OF AGE.FATALITY RATE OVER 10 YEARS OF AGE.
VACCINATED.UNVACCINATED.VACCINATED.UNVACCINATED.
Dewsbury2·232·12·618·7
Leicester0·014·01·07·8
Gloucester3·841·010·039·7

In view of such results as the above it is not surprising that the Royal Commission, in their majority report, summed up the advantages of vaccination as follows:

“(1) That it diminishes the liability to be attacked by the disease.

“(2) That it modifies the character of the disease, and renders it (a) less fatal, and (b) of a milder or less severe type.

“(3) That the protection it affords against attacks of the disease is greatest during the years immediately succeeding the operation of vaccination. It is impossible to fix with precision the length of this period of highest protection. Though not in all cases the same, if a period is to be fixed, it might, we think, fairly be said to cover in general a period of nine or ten years.

“(4) That after the lapse of the period of highest protective potency, the efficacy of vaccination to protect against attack rapidly diminishes, but that it is still considerable in the next quinquennium, and possibly never altogether ceases.

“(5) That its power to modify the character of the disease is also greatest in the period in which its power to protect from attack is greatest, but that its power thus to modify the disease does not diminish as rapidly as its protective influence against attacks, and its efficacy during the later periods of life to modify the disease is still very considerable.

“(6) That re-vaccination restores the protection which lapse of time has diminished, but the evidence shows that this protection again diminishes, and that, to ensure the highest degree of protection which vaccination can give, the operation should be at intervals repeated.

“(7) That the beneficial effects of vaccination are most experienced by those in whose case it has been most thorough. We think it may fairly be concluded that where the vaccine matter is inserted in three or four places, it is more effectual than when introduced into one or two places only—and that if the vaccination marks are of an area of half a square inch, they indicate a better state of protection than if their area be at all considerably below this.”