Review of Randomized Controlled Trials on Herbal Medicine for Influenza Prevention

Objective: The purpose of this study was to review randomized controlled trials (RCTs) on herbal medicine for the prevention of influenza.Methods: Literature searches were performed on eight databases: PubMed, EMBASE, Cochrane Library, CNKI, CiNii, OASIS, RISS, and ScienceOn. Studies in these databases were screened based on inclusion and exclusion criteria, and their details, including study design, participants, herbal medicine use, outcome measures, results, and adverse events, were analyzed.Results: A total of 2464 studies were searched, and 25 were finally included in this study. Among the selected studies, 19 evaluated the preventive effects of herbal medicine on influenza infection and demonstrated that herbal medicine reduced the incidence of influenza infection and symptoms. In six studies, the adjuvant effects of herbal medicine on antibody titer against the influenza virus after vaccination were investigated, and there were significant increases in H3N2 antibody titers after vaccination between the treatment and control groups in two studies.Conclusion: This study suggests that herbal medicine had a preventive effect on influenza infection and an adjuvant effect on H3N2 antibody titer after vaccination in the selected studies. The results of this study are expected to be used in the clinical application and design of clinical trials.