Probiotics Against Viruses; COVID-19 is a Paper Tiger: A Systematic Review

Background: Probiotics can improve immune function leading to the prevention and management of viral infections like SARS-CoV-2 infection (COVID-19 disease). Methods: We searched PubMed, EMBASE, Google Scholar, Science Direct, Scopus, and Web of Science up to May 2020 to identify interventional & observational studies documenting the effects of probiotics on incidence, severity, duration, and other clinical manifestations of viral infections, especially SARS-CoV-2-induced. Results: From a total of 91 records, 24 studies were obtained and classified into three domains based on the efficacy of probiotics on 1) shortening the period and severity of infections (n=9), 2) incidence (n=6), and 3) other clinical complications that may be followed by viral disorders (n=9). Identified probiotics have positive effects on the mentioned domains. Conclusion: Based on the evidence, some probiotic strains may be useful in SARS-CoV-2 infection; randomized trials are needed to show the facts.