Before making any commentary on these remarkable figures, it may be well to attend to what Watt had to say concerning them. He was satisfied that vaccination arrested smallpox, but it was plain that it did not arrest death, and he felt bound to find some explanation—
From every circumstance that has come under my observation, the efficacy of Vaccine Inoculation appeared certain. The experience of pretty extensive practice had confirmed me fully in this opinion. But still the question recurred, how are we to account for the same, or nearly the same, number of deaths under ten years of age? As no new disease has appeared, the deficiency occasioned by the want of Smallpox must have been made up by a greater mortality among the other diseases of children. Has it been equally divided among them, or has a greater share fallen to some than to others? To solve this question is the chief object of my inquiry.
To ascertain the fact, he divided the thirty years, 1783-1812, into five periods of six years each, and thus set forth the average proportionate mortalities—
| Years. | From Smallpox. | Measles. | Whooping Cough. | Children under Two. | Children under Ten. | Total, all Ages. | |
| 1783-1788 | 19·55 | ·93 | 4·51 | 39·40 | 53·48 | 9,994 | |
| 1789-1794 | 18·22 | 1·17 | 5·13 | 42·38 | 58·07 | 11,103 | |
| 1795-1800 | 18·70 | 2·10 | 5·36 | 38·82 | 54·48 | 9,991 | |
| 1801-1806 | 8·90 | 3·92 | 6·12 | 33·50 | 52·03 | 10,034 | |
| 1807-1812 | 3·90 | 10·76 | 5·57 | 35·89 | 55·69 | 13,354 |
The first three of these periods, 1783-1800, had passed before the Vaccine Inoculation could have had any influence [observes Watt]; in the fourth, 1801-1806, it had nearly reached its maximum; and in the last, 1807-1812, it may be said to have been pretty fully established, perhaps as much so as in any other city in the empire.
Vaccination having been introduced to Glasgow to save life, Where was the salvation? Smallpox had fallen off, but if its victims were merely assigned to other modes of death, where was the advantage? Watt continues—
The first thing which strikes the mind on surveying the preceding Table, is the vast diminution in the proportion of deaths by the Smallpox—a reduction from 19·55 to 3·90 per cent.; but the increase in the Measles column is still more remarkable—an increase from ·93 to 10·76 per cent. In Smallpox we have the deaths reduced to nearly a fifth of what they were twenty-five years ago, whilst in the same period, the deaths by Measles have increased more than eleven times. This is a fact so striking, that I am astonished it has not attracted the notice of older practitioners.
The greatest number of deaths from Smallpox in any one month during the last thirty years was 114 in October, 1791. In the following December they were 113. These are the only two instances in thirty years when the deaths by Smallpox amounted to 100 in a month. But these were slight visitations when compared with the ravages which have been committed in an equally short time by Measles. In May, 1803, the deaths by Measles alone amounted to 259, in June to 260, and in July to 118. In December, 1811, they amounted to 161, and in the January following to 130. What an amazing difference when we compare these numbers with 433, the sum of all the deaths by Measles in eighteen years preceding 1801! In the last five years 1430 have died of Measles in Glasgow.
This prodigious increase in the mortality from Measles was naturally referred by some observers to the practice of Vaccination, and Watt held there was ground for the assumption inasmuch as when Smallpox preceded Measles it made Measles milder—
When Measles was so prevalent and fatal in 1808, I was often told that it was owing to the Vaccine Inoculation; but this I considered an idle tale, the invention of those who were hostile to Cowpox. I could readily admit that more must die of Measles than formerly; for some of the weak and unhealthy, who would have died of Smallpox (saved from Smallpox) would fall a sacrifice to Measles; but I could not then go farther.