Background: The coronavirus disease 2019 (COVID-19) pandemic has caused a worldwide outbreak of respiratory illness. This review aims to evaluate the effectiveness and adverse events of herbal medicines for the treatment of COVID-19.
Methods: Twelve databases were searched through 12 May 2020. Randomized controlled trials (RCTs) and quasi-RCTs assessing the effects of herbal medicines for the treatment of COVID-19 were eligible. The study selection and data extraction were performed by two independent reviewers. The Cochrane risk of bias tool was used for the assessment of the risk of bias in all included RCTs. Mean differences (MDs), risk ratios (RRs) and odds ratios (ORs) with 95% confidence intervals (CIs) were calculated, and the effect sizes of the studies were pooled.
Results: Seven RCTs with a total of 855 patients were included. All included trials compared the combined therapy of herbal medicine with Western medicine to Western medicine alone. The combined therapy significantly improved the total effective rate (RR 1.23, 95% CI 1.13 to 1.34, p < 0.001), cough symptom disappearance rate (RR 1.45, 95% CI 1.12 to 1.89, p = 0.005), and sputum production symptom disappearance rate (RR 1.73, 95% CI 1.19 to 2.50, p = 0.004). Beneficial effects of the combined therapy were also seen in TCM syndrome score of cough (MD -1.18, 95% CI -1.34 to -1.03, p < 0.001), fever (MD -0.62, 95% CI -0.79 to -0.45, p < 0.001), dry and sore throat (MD -0.83, 95% CI -1.45 to -0.20, p = 0.009), and fatigue (MD -0.60, 95% CI -1.04 to -0.17, p = 0.007). The overall risk of bias of the included studies was unclear. No serious adverse events were reported.
Conclusion: Significant effects of the combined therapy of herbal medicine with Western medicine were found, and revealed the potential role of herbal medicine in treating COVID-19. More high-quality RCTs are needed to further validate the effectiveness and adverse events of herbal medicine in the treatment of COVID-19.
Keywords: COVID-19; complementary and alternative medicine; coronavirus disease; herbal medicine; systematic review.