Echinacea purpurea may help prevent respiratory tract infections during COVID-19 pandemic

The coronavirus disease 2019 (COVID-19) pandemic has had a significant impact on global healthcare systems and the world economy. In addition to common respiratory viral infections, novel variants of coronaviruses and influenza viruses continue to present a formidable challenge to human health and national healthcare systems. A new study published on the preprint server medRxiv* describes the results of using an extract of the medicinal plant Echinacea purpurea to treat non-severe cases of COVID-19.

Study: Echinacea purpurea for the Long-term Prevention of Viral Respiratory Tract Infections during COVID-19 Pandemic: A Randomized, Open, Controlled, Exploratory Clinical Study. Image Credit: Nataliia Kuznetcova /


Despite the rapid development of vaccines, which were initially touted as the key to ending the pandemic, a combination of human frailties and viral mutations has limited the efficacy of these interventions. Furthermore, new variants of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have emerged, such as the Delta variant, which is more infectious, associated with larger viral loads, and are capable of evading the human immune response elicited by both natural infection and vaccination.

Illustration of the intervention scheme showing phases of EF prevention (blue) interrupted by phases of breaks (grey) with study visits (V1-V7) for routine virus sampling.
Illustration of the intervention scheme showing phases of EF prevention (blue) interrupted by phases of breaks (grey) with study visits (V1-V7) for routine virus sampling.

All currently available vaccines reduce the number of severe COVID-19 cases, independent of virus strain and the time elapsed since vaccination. However, the same is not true of the number of infections in total or viral loads. This means that infections continue to occur and SARS-CoV-2 continues to be transmitted.

As a result, new therapies that are capable of arresting non-severe infections and reducing the transmission of SARS-CoV-2 by reducing the viral load in the nose and throat are urgently needed. E. purpurea is associated with broad-spectrum antiviral properties, including against coronaviruses. These properties have been demonstrated by the inhibition of infectivity of human coronaviruses in vitro by an extract from the root and herb.

In vitro studies on E. purpurea have also demonstrated the ability of this plant to modulate the immune response, reduce pro-inflammatory cytokines like tumor necrosis factor (TNF) and interleukin-1β (IL-1β).  

About the study

The current study focuses on the antiviral effects of this E. purpurea in the context of the current COVID-19 pandemic. Further, the researchers examine how and whether E. purpurea extracts could prevent and treat respiratory viral infections, especially SARS-CoV-2 infection.

A total of 120 volunteers were included in the current study, all of whom were Caucasian and had a mean age of 36 years. Notably, 36.7% of the participants were smokers. While three individuals received their first dose of a COVID-19 vaccine before their fourth visit, 12 were fully vaccinated by the end of the study and the treatment group reported greater than 90% compliance.

All study participants, who were initially healthy at the beginning of the study, were observed for 23 weeks. During the study period, 31% had tested positive for SARS-CoV-2 by polymerase chain reaction (PCR) testing or serology.

Study participants were divided into either the E. purpurea group or the control group. Study participants who received E. purpurea went through three prevention cycles of two, two, and one month. These participants took a total of three 800 milligrams (mg) E. purpurea extract each day, for a total dose of 2,400 mg/day.

Study findings

The results show that the extract potently reduced SARS-CoV-2 infections and viral loads, especially of enveloped viruses, as part of an overall reduction in respiratory virus infections. This corroborated earlier in vitro studies of E. purpurea.

In the E. purpurea group, there were 11 positive tests for any virus, which was compared to 29 reported in the control group, thus indicating a risk reduction by almost half. Of these, 5 and 14 were SARS-CoV-2 positive, respectively, thereby indicating that the risk of COVID-19 decreased by 63%. There were 10 and 14 episodes of reported symptoms, respectively, about half in each group being due to COVID-19.

The use of E. purpurea in an acute symptomatic episode led to a 99% reduction in viral load, while reducing the viral load by eight days overall, but about five days for SARS-CoV-2, compared to controls. Symptom severity was comparable in both groups; however, fever lasted only one day on average in individuals in the E. purpurea group as compared to 11 days for controls.

Other medications were used as required in both groups; however, medications related to respiratory symptoms were used to a lesser degree in the treatment group. Hospitalizations related to COVID-19 also fell with E. purpurea treatment, respectively, despite the fact that the treatment group had more underlying medical conditions.  


The use of E. purpurea over five months protected against 25% of all respiratory viruses, though this was not statistically significant, 50% of coronaviruses, and 63% of SARS-CoV-2 infections. Its preventive effects helped avert symptomatic respiratory tract infection by almost the same proportions as well, though the results did not achieve statistical significance.

These findings agree with those that report a reduction in respiratory infections with enveloped viruses by almost half. The plant extract E. purpurea has a very short half-life, which may indicate that treatment breaks should be minimized when possible.

At present, there is widespread interest in additional proven therapies that can help effectively reduce the SARS-CoV-2 viral load in the nose and throat and thus limit viral shedding by infected individuals, even when asymptomatic.

Our findings demonstrate that [E. purpurea] treatment during acute RTI episodes significantly reduced virus loads (all viruses and SARS-CoV-2) by more than 99%.”

The temporal track of viral clearance is not available, and decay of antiviral efficacy over time is not known at present. However, it appears that the cocktail of active components in this extract limit the ability of respiratory viruses to evade the antiviral effects. This is the case with the different variants of SARS-CoV-2 as well.

Thus, the commercial preparation of E. purpurea used in this study showed promising antiviral effects and reduced the risk of viral respiratory infections, including SARS-CoV-2. It produced marked reductions in the viral load in infected subjects.

“[It] offers a supportive addition to existing mandated treatments like vaccinations. Future confirmatory studies are warranted.”

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:
Dr. Liji Thomas

Written by

Dr. Liji Thomas

Dr. Liji Thomas is an OB-GYN, who graduated from the Government Medical College, University of Calicut, Kerala, in 2001. Liji practiced as a full-time consultant in obstetrics/gynecology in a private hospital for a few years following her graduation. She has counseled hundreds of patients facing issues from pregnancy-related problems and infertility, and has been in charge of over 2,000 deliveries, striving always to achieve a normal delivery rather than operative.


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