OM-85 BV is an immunomodulatory agent used for prevention of exacerbations in persons with chronic lung disease. We conducted a systematic review of OM-85 BV to evaluate its efficacy and safety. A systematic search for relevant articles was performed. Studies were included if they involved persons with chronic obstructive pulmonary disease or chronic bronchitis and were randomized to OM-85 BV or placebo. Investigators extracted data on study design, participant characteristics, and clinical outcomes. Thirteen trials involving 2066 individuals met inclusion criteria. Three trials enrolled an older, more homogenous population with chronic obstructive pulmonary disease. Utilizing quantitative pooled analysis in these studies, with one or more acute exacerbations as the endpoint, we found a non-statistically significant trend in favor of OM-85 BV [relative risk 0.83, 95% confidence interval 0.65-1.05]. Ten trials enrolled a heterogeneous population with chronic bronchitis. In these trials, exacerbation rates were less with OM-85 BV in 4 of 9 trials reporting this outcome. Varied results in the outcomes of hospitalization, symptom scores, and antibiotic or steroid use were found across studies. Withdrawals and adverse events were similar between OM-85 BV and placebo. While OM-85 BV is used to prevent exacerbations in persons with chronic lung disease, consistent evidence across multiple important outcomes does not exist to clearly demonstrate clinical benefit. Further randomized controlled trials enrolling large numbers of persons with well-defined COPD are necessary to confirm the effectiveness of this agent.