Herbal Medicine and COVID-19: Characteristics and Methodological Quality of Published Reviews

The literature on coronavirus disease 2019 (COVID-19) treatments, including herbal medicine, has expanded rapidly due to intense global interest. We conducted this scoping review to map the characteristics and assess the quality of systematically conducted reviews of herbal medicine and COVID-19 published during the pandemic era. Electronic databases were searched to identify published systematic reviews and other research synthesis articles relating to herbal medicine vis-a-vis COVID-19 from 2020 to 2022. Forty-eight articles were included. Most were systematic reviews (SR) and/or meta-analyses (MA) on Chinese herbal medicine for clinical treatment during the acute phases of COVID-19 (44%). Regarding adherence to a measurement tool to assess systematic reviews (AMSTAR-2) critical items, only one-third (n = 15) reported an a priori protocol, while 21% (n = 10) presented a comprehensive literature search strategy. When analysed by type of review, SR/MA (n = 23) of clinical interventions had better than the overall average adherence rate in having a pre-registered protocol (87%, n = 20) and comprehensive literature search strategy (45%, n = 9). Exploratory analysis showed that most articles reported search results from at least two established electronic databases. Risk of bias assessment was performed in almost all SR/MA though there was limited exploration of any potential sources of heterogeneity. Overall, there is a need to improve the methodological design and implementation of systematically conducted reviews of herbal medicine in general to enhance the robustness and reliability of findings, especially given the rapid expansion of literature during unique circumstances such as the COVID-19 pandemic.