Probiotics for Preventing Upper Respiratory Tract Infections in Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background. Upper respiratory tract infections (URTIs) are common and burdensome infectious illness. Several trials have reported that probiotics can prevent URTIs in adults. Objectives. To evaluate the efficacy and safety of probiotics in the prevention of URTIs in adults. Methods. PubMed, Web of Science, Embase, and Cochrane Library were searched for reports published from database inception to May 14, 2020. Randomized controlled trials (RCTs) comparing probiotics with placebo for the prevention of URTIs in adults were included. Results. Six RCTs with 1551 participants were included. Compared with the placebo group, the probiotics intervention group significantly reduced the incidence of URTI episodes (RR: 0.77; 95% CI: 0.68 to 0.87; P