Protective effect of Bacillus Calmette Guerin (BCG) against leprosy: a population-based case-control study in Nagpur, India.

A population-based pair-matched case-control study was carried out in an urban community, Nagpur, India, to estimate the effectiveness of BCG vaccination in the prevention of leprosy. The study included 212 cases of leprosy (diagnosed by WHO criteria), below the age of 35 years, detected during a leprosy survey conducted by the Government of Maharashtra over a population of 20,03,325. Each case was pair-matched with one neighbourhood control for age, sex and socioeconomic status. A significant protective association between BCG and leprosy was observed (OR = 0.40, 95% CI = 0.23-0.68). The overall vaccine effectiveness (VE) was estimated to be 60% (95% CI = 32-77). The BCG effectiveness against multi-bacillary and paucibacillary leprosy was 72% (95% CI = 35-88) and 45% (95% CI = 3-73), respectively. Vaccine was more effective during the first decade of life, among females and in lower socioeconomic strata. The overall prevented fraction was 39% (95% CI = 16-58). In conclusion, this first ever population-based case control study performed in Central India, identified a beneficial role of BCG vaccination in prevention of leprosy in study population.