Results
Our study included 13 large-scale studies involving a total of 260,029 participants. Our quantitative analysis found that administering BCG vaccine in early childhood significantly reduced the risk of developing asthma (OR 0.74, 95%CI 0.61 to 0.91), but there was no association between early childhood BCG vaccination and the risk of developing eczema (OR 0.87, 95%CI 0.68 to 1.11) or rhinitis. (OR 1.03, 95%CI 0.87 to 1.22). The effect of BCG vaccination with asthma was evident especially in European countries (OR 0.59, 95%CI 0.40 to 0.88) and American countries (OR 0.90, 95%CI 0.82 to 0.98)