BCG vaccination and pulmonary tuberculosis in Quebec.

The BCG vaccination program officially set up in 1949 in the Province of Quebec has been retrospectively evaluated for the period from 1956 to 1961. Two series of age groups were studied, 0-14 and 15-29, each comprising populations of several hundred thousand. At the beginning and the end of the period, the rates of primary vaccination were, in percentages of viable births, from 40 to 47.8 and, in cumulative percentages, for the 0 to 14 year age group, from 39.98 to 53.41, and for the 0 to 29 year age group, from 29.22 to 45.98.During this period, the ratios between the yearly rates of incidence of new cases of pulmonary tuberculosis per 100,000 in vaccinated and non-vaccinated individuals ranged from 1-2.5 to 1-3.5 within the age group 0-14 years and from 1-4.5 to 1-7 within the age group 15-29 years. When only the incidence of the more severe forms of tuberculosis is considered, the ratios ranged from 1-3.7 to 1-6.0 for the younger group and from 1-5.3 to 1-7.6 for the older one.Mortality from pulmonary tuberculosis was practically non-existent in the vaccinated groups and decreased from 2.5 to 1.3 per 100,000 population in the non-vaccinated groups.