Case-control study of BCG vaccination as a risk factor for leprosy and tuberculosis in western Kenya.

A case-control study was carried out in western Kenya to measure the protection imparted by BCG against leprosy and tuberculosis. The study involved 69 newly diagnosed leprosy cases, 238 age-, sex- and neighborhood-matched controls, and 144 newly diagnosed, sputum-smear-positive tuberculosis cases along with 432 age-, sex- and neighborhood-matched controls. Information on BCG vaccination history was inferred from scars. Using matched analysis, the protection imparted by BCG against leprosy was estimated to be 81% [95% confidence interval (CI) = 67-90] with no apparent difference in protection against paucibacillary [vaccine efficacy (VE) = 83%, 95% CI = 58-92] and multibacillary leprosy (VE = 76%; 95% CI = 30-91). The effectiveness against tuberculosis was appreciably lower (VE = 22%) and was not statistically significant (95% CI = -20-51).