This meta-analysis reviewed 14 prospective trials and 12 case-control studies to analyze the efficacy of the BCG vaccine in preventing tuberculosis (TB). The analysis found that BCG vaccination was 51% effective at preventing TB based on data from 13 trials. Case-control studies also indicated a 50% protective effect against TB from BCG vaccination. However, there was significant heterogeneity between the studies with efficacy ranging from no benefit to 80% protection. Geographic location and study validity scores explained some of the differences in results between studies.