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Gabrielle Settles
By Gabrielle Settles February 2, 2022

Ivermectin study showed ‘antiviral effect,’ which is not the same as being effective against omicron

If Your Time is short

  • Reuters corrected a Jan. 31 article that originally reported that a Japanese study found ivermectin to be effective against omicron in human participants in a clinical trial. It was actually non-clinical laboratory research that found the drug to have "antiviral properties." It did not involve humans.

  • Ivermectin is not authorized for use against COVID-19 in the U.S. There are many ongoing studies into its use, including in Japan.

Spotify podcaster and vaccination skeptic Joe Rogan was quick to share a headline on Twitter that portrayed the anti-parasitic drug ivermectin as effective against the omicron variant of COVID-19. 

What Rogan didn’t share was a prominent correction that followed: The drug was found only to have an "antiviral" effect, and did not involve a clinical study of humans. 

Rogan shared a tweet from that said: "JUST IN - Japan's Kowa in partnership with Kitasato University at Tokyo Medical University says ivermectin is effective against Omicron in phase III trial." 

"Well, lookie here…" Rogan wrote in a since-deleted quote-tweet. Rogan had taken the drug when he contracted COVID-19 in September, he said at the time. was pointing to a Reuters report that said Japanese pharmaceutical company Kowa and Tokyo-based Kitasato University found ivermectin to be effective against omicron in Phase III clinical trials, which are conducted with human participants.

Reuters rewrote the story with a correction.

But the uncorrected claim had already spread across Twitter, with The Blaze senior editor Daniel Horowitz and Fox News host Laura Ingraham tweeting similar claims.

What Kowa actually said was that scientists using non-clinical research found ivermectin to have an "antiviral effect." Non-clinical lab results are not the same as clinical studies, and just because something has an antiviral effect does not mean it is effective. Non-clinical studies involve experiments that are typically conducted under lab conditions, like a test tube, according to the U.S. Food and Drug Administration.

Reuters said its journalists "misinterpreted the Kowa announcement"  in a comment to Washington Post media critic Eric Wemple. Wemple said he asked why the study’s "antiviral" finding was newsworthy even after the correction.

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"The antiviral capabilities of ivermectin against SARS-CoV-2 in a test-tube environment are not a matter of breaking news: Research dating to 2020 showed that ‘a single dose of ivermectin was able to reduce the replication of an Australian isolate of SARS-CoV-2 in Vero/hSLAM cells by 5000-fold,’" Wemple wrote.

Kowa said on Jan. 31 that it is testing ivermectin in Phase III clinical trials. Per the FDA, each phase of a clinical trial involves a larger number of people, and phase III can usually involve up to 3,000. Participants are randomly assigned the drug or a placebo.

"We believe that it is our mission as a pharmaceutical company to contribute to the treatment of new coronavirus infections and protect the health of the people, and we are conducting clinical trials to confirm the efficacy and safety of ivermectin for new coronavirus infections," the company said.

With multiple studies around the world under way, ivermectin is still not authorized to treat or prevent COVID-19 in the U.S. 

"To date, published clinical trials have shown mixed results," Chanapa Tantibanchachai, an FDA spokesperson, wrote in an email to PolitiFact for a Jan. 28 fact-check.

Tantibanchachai said that ivermectin can be prescribed by doctors for COVID-19 if they deem it appropriate, though "the safety and efficacy" hasn’t been established. 

The drug has many advocates who see it as an over-the-counter alternative for preventing or treating COVID-19; they tend to ignore contrary evidence or tout flawed research. Last year, poison control centers received a surge of calls from people who self-medicated with the drug. 

The World Health Organization said it should only be used in clinical trials until more data is found. 

The updated Reuters story points out that hydroxychloroquine, an antimalarial drug also used to treat lupus, had been touted as a potential treatment for COVID-19 by former President Donald Trump and others after promising lab results. Subsequent studies on humans did not find a benefit. 

Claims that new research shows ivermectin is effective for treating COVID-19 were based on a reporting error. We rate them False.

Our Sources

Daniel Dale Twitter post, Jan. 31, 2022, Twitter post, Jan. 31, 2022

Daniel Horowitz Twitter post, Jan. 30, 2022

Laura Ingraham Twitter post, Jan. 31, 2022

 U.S. Food and Drug Administration, Definitions, accessed Feb. 1, 2022

The Washington Post, Opinion: Reuters botches article on ivermectin and omicron, Feb. 1, 2022

Arieh Kovler, Twitter post, Jan. 31, 2022

FDA, Why You Should Not Use Ivermectin to Treat or Prevent COVID-19, Dec. 10, 2021

NPR, Poison Control Centers Are Fielding A Surge Of Ivermectin Overdose Calls, Sept. 4, 2021

PolitiFact, Study in Brazil on ivermectin as a COVID-19 prevention is flawed, experts say, Jan. 28, 2022

PolitiFact, Fact-checking claim about the use of ivermectin to treat COVID-19

World Health Organization, WHO advises that ivermectin only be used to treat COVID-19 within clinical trials, Mar. 31, 2021

Reuters, Ivermectin shows ‘antiviral effect’ against COVID, Japanese company says, Jan. 31, 2022

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Ivermectin study showed ‘antiviral effect,’ which is not the same as being effective against omicron

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