Heiser and Leach,1 in their article entitled "Vaccination in the Philippines Still Effective," presented a summarized study regarding the possible causation of the outbreak of smallpox in 1918, and of the casualties of the disease up to 1920. In the same article, some of the many difficulties encountered in the way of vaccination were pointed out. In the present paper I shall attempt to supplement what was said on the immunizing value of antivariolar vaccination, as observed in the last two years.
For the purpose of this study, an analysis of all available statistics, on the morbidity and the mortality of smallpox and on the results of vaccination during 1921 and 1922, has been made.
MORBIDITY AND MORTALITY RATES IN GENERAL
In Manila, where there had been preformed every year higher proportions of successful vaccinations, smallpox completely disappeared in 1921 and 1922; the last five cases, with three deaths,