The BCG controversy: a reappraisal of the protective effect against tuberculosis and leprosy.

BCG (Bacillus Calmette Guerin) vaccine remains a highly controversial method of preventing tuberculosis and leprosy despite more than eighty years of use. The protective effect against tuberculosis observed in various studies ranged from -56% to 98%. Case-control studies carried out at Nagpur reported moderate effectiveness of BCG vaccination in prevention of tuberculosis. Its effectiveness was higher against extra-pulmonary tuberculosis. The summary protective effects obtained from meta-analysis of trials, cohort studies and case-control studies of BCG vaccination and tuberculosis were 51 (33-64), 76 (63-85), and 65 (57-72) percent respectively. The case-control studies carried out at Nagpur also demonstrated a significant protective association between BCG vaccination and leprosy. The summary protective effects obtained from meta-analysis of trials, cohort studies and case-control studies of BCG vaccination and leprosy were 43 (27-55), 62 (53-69), and 59 (46-68) percent respectively. The results of the current study and systematic review thus supported arguments favoring use of BCG vaccine for prevention of tuberculosis and leprosy.