ABSTRACT
Echinacea purpurea has been shown to broadly inhibit coronaviruses and SARS-CoV-2 in vitro. This review discusses the available clinical evidence from randomized, blinded and controlled human studies. Two RCTs capturing incidence of viral respiratory tract infections during Echinacea preventative treatment were identified including coronavirus infections. Incidence and/or viral loads were measured by RT-PCR and symptom severity was recorded. In a first study, Jawad et al. collected nasopharyngeal swabs from adults (N = 755) over 4 months of continuous prevention. Overall, 24 and 47 enveloped virus infections occurred, including 21 and 33 coronavirus detections (229E; HKU1; OC43) with Echinaforce® extract (2400 mg daily) and placebo, respectively (p = 0.0114). In a separate study, Ogal et al. administered the same extract (1200 mg) or control for 4 months to children (4-12 years) (N = 203). Echinacea reduced the incidence of enveloped virus infections from 47 to 29 (p = 0.0038) whereas 11 and 13 coronavirus detections (229E, OC43, NL63) were counted (p > 0.05). Respiratory symptoms during coronavirus infections were significantly lower with area-under-curve AUC = 75.8 (+/-50.24) versus 27.1 (+/-21.27) score points (p = 0.0036). Importantly, viral loads in nasal secretions were significantly reduced by 98.5% in the Echinacea group, with Ct-values 31.1 [95% CI 26.3; 35.9] versus 25.0 [95% CI 20.5; 29.5] in the control group (p = 0.0479). Results from clinical studies confirm the antiviral activity found for Echinacea in vitro, embracing enveloped respiratory pathogens and therefore coronaviruses as well. Substantiating results from a new, completed study seem to extrapolate these effects to the prevention of SARS-CoV-2 infections. As hypothesized, the established broad antiviral activity of Echinacea extract appears to be inclusive for SARS-CoV-2.