Experience with BCG Vaccine in the Control of Tuberculosis among North American Indians

Abstract

The efficacy of BCG in lowering the incidence and mortality of tuberculosis in America Indians was tested on 3007 persons on 7 reservations in Arizona Wyoming North and South Dakota and Alaska in a double-blind design. Participants were selected on the basis of negative tuberculin reaction and chest x-rays but presence of a Koch reaction could not be determined in controls. The test groups received 0.1-0.15 ml BCG intracutaneously and the controls saline; all were followed for 6 years with annual tuberculin tests and chest x-rays. The groups did not differ in age amount of exposure to tuberculosis or follow-up. Mortality in the control group was higher than in the vaccinated group as judged by number of deaths 60 vs. 43 and by death rate per 1000 person-years 7.2 vs. 3.8. 28 deaths were attributed to tuberculosis in the controls compared to 4 among the BCG groups. Severity of infection was greater in controls including numbers of extrapulmonary tuberculosis advanced pulmonary lesions minimal lesions and enlarged hilar glands. Incidence of new cases of tuberculosis decreased with time in the treated group while that in controls remained constant. There was some variation in effectiveness of the different lots of vaccine.