Some tried to account for the manifest failure of vaccination on the supposition that the original virus had lost its force in transmission from arm to arm, but Thomson would not allow that it had deteriorated. He said—
The Vaccine Virus used in Edinburgh for a series of eighteen years produces exactly the same appearances as are delineated by Dr. Jenner as characteristic of Cowpox. I know, also, that the appearances of the vaccine vesicle produced by this matter, which must have passed through a succession of at least 900 individuals, agree exactly with those exhibited by vesicles produced by inoculation, with the more recent equine matter with which I have been, lately favoured by Dr. Jenner.
The latter words are noteworthy. When Jenner’s ascription of the origin of Cowpox in Horsegrease is referred to, the answer frequently is, that Jenner was mistaken, and that he did not persist in his opinion. It is true that he did preserve a judicious silence about horsegrease when he saw that it would mar rather than make his fortune. But when he obtained all he was likely to get, he resumed the expression of his original opinion, and used and diffused what he described as horsegrease; and the vesicles raised by the virus, and the cicatrices which remained were identical with those induced by so-called Cowpox.
Another point developed in Thomson’s evidence was the mistake made crediting vaccination with the prevention of smallpox where there was no smallpox to prevent. The victories ascribed to vaccination were victories either over an imaginary or a retreating enemy. We cannot too firmly insist upon this point in presence of the claim continually advanced for the subjugation of smallpox by vaccination. For some cause undefined, and, probably in its full extent, undiscoverable, a subsidence of smallpox over the whole of Europe set in toward the close of last century, and continued during the early years of the present; and to this subsidence the favour that vaccination met with was largely due. The decline in the disease concurrently with the introduction of vaccination, was ascribed to vaccination, although the decline prevailed among an overwhelming majority who had never received vaccination. To make good the claim for vaccination it would have been necessary to maintain that the vaccine rite, as applied to 2 or 3 per cent. of Europeans, effected the salvation of 98 or 97 per cent. For example, a great point was made by Jenner and his friends of the extinction of smallpox in Vienna, according to the following table—
| Years. | Total Deaths. | From Smallpox. | |||
| 1791-1800 | average | 14,600 | 835 | or one in | 17½ |
| 1801 | 15,181 | 164 | 93 | ||
| 1802 | 14,522 | 61 | 238 | ||
| 1803 | 14,383 | 27 | 582 | ||
| 1804 | 14,035 | 2 | 7,017 |
Yet it was never pretended that in these years more than a fraction of the Viennese were vaccinated, or that the death-rate of the city was reduced by the disappearance of smallpox. The like fatuity characterised the whole of the vaccinators’ statistics. Smallpox had declined, therefore, they argued, vaccination is the cause of the decline, and multitudes were convinced by the illicit logic. When vaccination was, however, brought to the test of epidemic smallpox, its inefficacy became manifest, and thus Thomson had to avow, as the result of his experience in the Edinburgh epidemic of 1818-19—
It is to the severity of this epidemic, I am convinced, that we ought to attribute the greatness of the number of the vaccinated who have been attacked by it, and not to any deterioration in the qualities of the Cowpox Virus, or to any defects in the manner in which it has been employed. Had a variolous constitution of the atmosphere, similar to that which we have lately experienced, existed at the time Dr. Jenner brought forward his discovery, it may be doubted whether it ever could have obtained the confidence of the public.
Such was the article which Jenner “put down for 100,000 deaths at least.” Yet neither Jeffrey nor Thomson renounced vaccination. They agreed that whilst it could no longer be trusted to prevent smallpox, it made the disease milder in those it attacked. When a cherished belief is surrendered, it is rarely unconditionally: it is only by degrees that full concession is made unto truth.
FOOTNOTE:
[224] An Account of the Varioloid Epidemic which has lately prevailed in Edinburgh and other Parts of Scotland; with Observations on the Identity of Chickenpox with Modified Smallpox. By John Thomson, M.D. London, 1820. Pp. 400.