Ivermectin, an anti-parasitic drug popularized as a way to treat COVID-19 at home despite warnings from the Food and Drug Administration, was not shown to have a meaningful effect in shortening symptoms or decreasing the rate of hospitalizations or deaths, according to clinical trial results published Sunday .

The study, led by scientists from Duke University and Vanderbilt University , included 1,591 participants who received either 400 mcg/kg of the ivermectin, which is often used to treat livestock, or a placebo. Forty-seven percent of the participants said they had received at least two doses of a COVID vaccine.

This clinical trial has not yet been peer-reviewed.

The main measure of effectiveness of ivermectin used in the study was based on time to sustained recovery, which was defined as three consecutive days with no COVID symptoms. The key secondary outcome included a composite of hospitalization or death by day 28, wrote Duke Clinical Research Institutes Susanna Naggie, MD, MHS, one of the researchers involved in the study, in the document reviewing the studys results.

Taking ivermectin for three days resulted in less than one day of shortening of symptoms and did not lower incidence of hospitalization or death among outpatients with COVID-19 in the United States during the delta and omicron variant time periods, the document stated.

This clinical trial was part of the Accelerating COVID-19 Therapeutic Interventions and Vaccines (ACTIV)-6 study group, which investigates whether certain drugs approved by the FDA could be effective in treating patients at or over 30 years old with early mild-to-moderate COVID.

ACTIV-6 adds to the growing evidence that there is not a clinically relevant treatment effect of ivermectin at this dose and duration, Naggie wrote. While those with severe symptoms at baseline appeared to have beneficial treatment effect with ivermectin as compared with placebo, this subgroup was small, thus these findings should be considered exploratory.

The conclusion of this study is consistent with findings of another large clinical trial in Brazil , which was published by the New England Journal of Medicine in May .

Treatment with ivermectin did not result in a lower incidence of medical admission to a hospital due to progression of COVID-19 or of prolonged emergency department observation among outpatients with an early diagnosis of COVID-19, those researchers concluded.

Despite the lack of proof that the drug has a substantial effect against COVID, ivermectin has had prominent boosters, including podcaster Joe Rogan.

Rogan shared a story on Twitter in February inaccurately claiming the drug was effective against the omicron variant in a phase III clinical trial. Rogan deleted the tweet after this turned out to be incorrect .

Last year, Rogan said he took the drug after he tested positive for COVID in September 2021 as a treatment.

A month earlier, the FDA had tweeted warning people against taking self-treating with ivermectin, which is commonly used on animals.

You are not a horse. You are not a cow. Seriously, yall. Stop it, the agency tweeted in August 2021 .

The FDA had also published a detailed post on their website explaining why Americans should stay away from the drug.

In Arkansas, inmates filed a lawsuit against a doctor who unknowingly prescribed the drug to them as a COVID treatment. A northwest county in the state though subsequently issued a resolution praising the physician in February.