Data collection process
Data including study author(s), country of publication, sample size (n ), age range, microorganism(s) of interest, treatment dosage, mode, and treatment length, and results for both the experimental and placebo groups were tabulated in an Excel sheet. Three reviewers independently assessed the risk of bias assessment using the Cochrane risk of bias tool version 2.0. The outcome for efficacy and safety were tabulated by three authors and independently reviewed by the 4th author. Original investigators were contacted via email to seek unreported or underreported information.