Protective effect of bacillus Calmette Guerin (BCG) vaccine in the prevention of leprosy: a meta-analysis.

BACKGROUND Although the role of bacillus Calmette Guerin (BCG) vaccine in the prevention of leprosy was hypothesized as early as 1939, its level of protective effect remained controversial. AIM As a meta-analysis systematically combines the results from different studies, we summarize the protective effect of BCG vaccine in prevention of leprosy using meta-analytic procedures. METHODS Our search strategy included a computerized literature search, snowballing technique to identify potential studies, review of previously compiled lists of BCG studies and articles, contacting experts on BCG vaccination and manual search to locate articles in non-indexed journals. The present meta-analysis included 22 studies (6 trials, 2 cohort studies and 14 case-control studies) on the role of BCG vaccine in the prevention of leprosy. The random effects model as described by DerSimonian and Laird was used to summarize the effect measures. For each summarization, a Chi-square test of heterogeneity was estimated. To strengthen the viewpoint further additional information from the studies which were not included in meta-analysis, was also utilized. RESULTS The summary protective effects calculated from trials, cohort studies and case-control studies were 43 (27-55), 62 (53-69) and 58 (47-67)% respectively, which were statistically significant. These estimates confirmed the protective association between BCG vaccination and leprosy. Review of 29 studies focusing on the role of BCG vaccination in the prevention of leprosy revealed that not a single study reported a negative protective effect. Thirteen (44.8%) studies demonstrated greater than or equal to 50% efficacy/effectiveness. CONCLUSION There is sufficient and convincing evidence of the protective effect of BCG vaccine against leprosy, as reflected from the meta-analysis and overall review of 29 studies of BCG vaccination and leprosy.