Long-term efficacy of BCG vaccine in American Indians and Alaska Natives: A 60-year follow-up study

DESIGN: Retrospective record review using Indian Health Service records, tuberculosis registries, death certificates, and supplemental interviews with trial participants. SETTING AND PARTICIPANTS: Follow-up for the period 1948-1998 among American Indians and Alaska Natives who participated in a placebo-controlled BCG vaccine trial during 1935-1938 and who were still at risk of developing tuberculosis. Data from 1483 participants in the BCG vaccine group and 1309 in the placebo group were analyzed. RESULTS: The overall incidence of tuberculosis was 66 and 138 cases per 100 000 person-years in the BCG vaccine and placebo groups, respectively, for an estimate of vaccine efficacy of 52% (95% confidence interval, 27%-69%). Adjustments for age at vaccination, tribe, subsequent BCG vaccination, chronic medical illness, isoniazid use, and bacille Calmette-GuÃƒÂ©rin strain did not substantially affect vaccine efficacy. There was slight but not statistically significant waning of the efficacy of BCG vaccination over time, greater among men than women. Mortality rates for other reasons than tuberculosis were higher in the placebo group. There were higher rates of diabetes and renal failure in the unvaccinated group.