Insights into add-on effectiveness of Chinese herbal formulae in COVID-19: An overview of systematic reviews

• Chinese herbal formulae (CHF) are a widely used adjunctive in COVID-19 management. • Overview of 8 reviews (6860 patients) evaluates CHF add-on effects rigorously. • CHFs may help in reducing mortality, severity of disease and adverse events. Coronavirus Disease 2019 (COVID-19) has rapidly spread worldwide, overwhelming healthcare systems. Numerous clinical trials have explored the efficacy of Chinese herbal formulae (CHFs) in treating COVID-19, resulting in a surge of systematic reviews (SRs). This review critically evaluates the additive effectiveness of CHFs for COVID-19, aiming to provide a robust foundation for high-quality research and integrated therapeutic strategies. This PRISMA-compliant review was registered on PROSPERO. We included SRs assessed oral CHFs combined with guideline recommended Standard Treatment (ST), versus ST in patients with COVID-19 patients. Primary outcomes included clinical improvement (e.g., days without ventilator support) and deterioration (e.g., new need for oxygen therapy). PubMed, Cochrane Library, Embase, Sinomed, CNKI, Wanfang, and VIP were searched from inception to July 1, 2024, for SRs (Cochrane/non-Cochrane) of RCTs reporting predefined outcomes. Secondary meta-analyses were conducted using RevMan 5.3, with methodological quality and evidence certainty assessed via AMSTAR-II and GRADE. Eight SRs (6860 cases) were included. Meta-analyses showed that CHF combined with ST outperformed ST alone in reducing all-cause mortality (RR = 0.27, 95 %CI [0.08–0.96], P = 0.04), adverse events (RR = 0.34, 95 %CI [0.20–0.59], P < 0.0001), severe case conversion (RR = 0.33, 95 %CI [0.17–0.66], P = 0.002), and improving pulmonary imaging (RR = 1.28, 95 %CI [1.12–1.46], P = 0.0003). No significant differences were observed in clinical symptom recovery rates (cough) or recovery times (cough and fatigue). Bubble plots suggested weak to moderate effects of specific CHFs (e.g., Buzhongyiqi Decoction, Maxingshigan-Weijing Decoction ) on viral clearance, severe case conversion, adverse events, and pulmonary imaging. Comprehensive analyses indicated that CHFs showed good add-on effect in treating COVID-19. However, it is important to note that the overall quality of evidence in these studies is generally low, and further high-quality clinical trials are needed to validate these findings.