Herbal medicine for COVID-19: An overview of systematic reviews and meta-analysis

As coronavirus disease 2019 (COVID-19) continues to spread throughout countries, researchers and scientific groups have published a large number of scientific papers examining effective treatments and prevention strategies for COVID-19, including herbal medicine. It has become difficult to navigate the increasing volume of scientific material on the pandemic, and critical appraisal of these outcomes is needed. This overview of systematic reviews (SRs) aims to synthesize evidence from SRs and summarize the effects of herbal medicine interventions in the treatment of COVID-19.

Four databases were searched from inception up to October 20, 2021. SRs analyzing primary studies of the efficacy of herbal medications for treating COVID-19 were included. Two reviewers selected the studies and retrieved the data independently. The AMSTAR 2 (A Measurement Tool to Assess Systematic Reviews) was used to assess the methodological quality of the included SRs.

A total of 21 SRs on herbal medicine treatments for COVID-19 were included. All SRs were published between May 2020 and September 2021. Thirteen of the SRs included only randomized controlled trials (RCTs), whereas the remaining eight included evidence from nonrandomized trials in addition to RCTs, with a significant overlap identified across the RCTs. Twelve SRs concluded that existing evidence was insufficient to form a definite judgment, nine found that herbal therapy was useful, and none indicated that herbal medicine had no benefit. The AMSTAR 2 tool revealed that the methodological quality of the included SRs was generally low.

In this overview of SRs, we reviewed herbal medicine-related evidence from 21 SRs that were published after the outbreak of COVID-19. This study shows that while there is considerable evidence demonstrating the advantages of herbal medicine interventions, the quality of the evidence is inadequate to provide solid and accurate judgments about the effectiveness of herbal medicine therapies for COVID-19. Despite the crisis caused by the pandemic, clinical studies and SRs should comply with established methodological standards.