Smallpox in London: factors in the decline of the disease in the nineteenth century.

THE decline of smallpox in Britain in the nineteenth century has long been recognized as a feature of the history of mortality in that period. The Royal Commission on Smallpox and Fever Hospitals of 1882, for example, traced the beginnings of this decline as far back as the 1780s.' Contemporaries, and historians subsequently, generally accepted that vaccination and its variants were the cause of the decline. Peter Razzell has suggested that "virtually all of the population" in the first half of the nineteenth century was protected by either vaccination or inoculation.2 Others are more cautious: Thomas McKeown, with reservations, appears to accept the view of "most epidemiologists" that vaccination was responsible for the decline of the disease.3 Gwendoline Ayers noted that while the "ebb of classical smallpox" in England can be traced as a long-term decline with peaks, the reasons for its final disappearance as a native disease have been "variously and incompletely assessed".4 Cyril Dixon, in his authoritative Smallpox, is even more cautious, seeming to suggest a decline in the virulence of the native smallpox strain, followed, in the early years of the twentieth century, by the emergence on the American continent of a very mild strain of the disease, variola minor, which eventually superseded the more deadly, and hitherto dominant, variola major. I More recently, Stuart Fraser has described smallpox prevention in Leicester, "probably the first" community in which "measures other than vaccination were introduced successfully to eradicate the disease".6 Three elements can thus be discerned in attempting to explain the decline of the disease. First, variations in the virulence of the virus strain; second, vaccination; third, measures other than vaccination taken to control the spread of the disease. Of these, the question of virulence must in the first instance be important, even though the long confusion of smallpox and chickenpox makes accuracy difficult.7 Razzell, following *Anne Hardy, MA, DPhil, Nuffield College, Oxford OX I INF.