A Prominent Study Said Ivermectin Prevents COVID, But The Data Is Suspect
An influential study from Argentina has been used to argue that ivermectin prevents COVID 100% of the time — but its inconsistencies have led experts to question if it could have actually happened as advertised.
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For anti-vaccine activists, the clinical trial results couldn’t have been better. The drug ivermectin, scientists in Argentina announced last year, prevented 100% of COVID-19 infections.
That glowing finding helped spark a craze for the decades-old medication, which is normally used to delouse people and deworm livestock, and drive the perception that it is a silver bullet against the pandemic.
“If you take it, you will not get sick,” an ivermectin-boosting physician told a Senate committee in December, describing it as a “wonder drug” and citing in part the trial “from Argentina.”
But there are signs that at least some of the experiments — as written up in a paper published in November — didn’t happen as advertised. After BuzzFeed News raised questions about how the study’s data was collected and analyzed, a representative from the Journal of Biomedical Research and Clinical Investigation, which published the results, said late Monday, “We will remove the paper temporarily.” A link was removed from the table of contents — but was reinstated by Thursday. The journal’s explanation, provided after this story was published, was that the author “informed us that he has already provided the evidence of his study to the media.”
The numbers, genders, and ages of the study’s participants were inconsistent. A hospital named in the paper as taking part in the experiments said it has no record of it happening. Health officials in the province of Buenos Aires have also said that they also have no record of the study receiving local approval.
And the researcher overseeing the project, Hector Carvallo, a retired endocrinologist and professor of internal medicine at the University of Buenos Aires, has declined to widely share his data — including with one of his own collaborators, emails show.
In short, independent experts told BuzzFeed News, the oft-cited study has so many red flags that it is, at best, unreliable.
“There is no way in which I could see a trial that actually occurred producing a pattern like this,” said Kyle Sheldrick, a doctor in Sydney and one of the critics who brought the study’s discrepancies to light.
Carvallo, 64, said the study was real. “We would never make up a study because it’s not ethical,” he told BuzzFeed News.
In an interview, Carvallo said he supports vaccines and that he himself is immunized. “What I want for ivermectin is to be considered as another possibility among the repurposed drugs. Not the best one, not the only one, just another one,” he said from Buenos Aires province. “And not to be considered a challenge to vaccines. That would be stupid because they are different.”
But others say that at a time of a global crisis, when vaccination rates are slumping in the face of a relentless virus, Carvallo’s research is being used to give desperate people false, and potentially dangerous, hope about the miraculous properties of a drug proven only to help kill parasites.
“The thing that really worries me is it’s being explicitly used as an alternative to vaccines by some people,” Sheldrick said.
A year after the world became fixated on hydroxychloroquine, ivermectin has shaped up to be the latest unproven cure to go viral. The FDA, the CDC, the World Health Organization, and even Merck, an ivermectin manufacturer, have warned against taking it for COVID. No reliable evidence shows that it works as a cure or preventative, according to a late July comprehensive analysis of randomized controlled trials, which wouldn’t have included the Argentine study. Scientists who last month announced the results of another major trial said ivermectin showed “no effect whatsoever” as a treatment.
Nevertheless, buoyed by the dual rise of the Delta variant and vaccine skepticism, ivermectin hype has reached a global fever pitch. Politicians from Brazil to Malaysia are pushing it. Feed stores are sold out, and prices are soaring. In Facebook groups and subreddits, people are swapping dosing tips and saying they’d rather eat horse paste than get vaccinated. The hunt for suddenly scarce ivermectin has led some to America’s Frontline Doctors, the group that erroneously touted hydroxychloroquine as a “cure” on the US Supreme Court steps.
Ivermectin prescriptions in the US are up 24-fold, according to the CDC, and poison control centers from Alabama to Mississippi have been flooded with calls about side effects and overdoses. One adult who drank an ivermectin injection meant for cattle, the CDC said, wound up hospitalized with confusion, drowsiness, hallucinations, abnormal breathing, and tremors.
Discovered in the late 1970s, ivermectin is approved by the FDA to treat a variety of parasitic conditions, such as river blindness, intestinal worms, and head lice. It’s also used by veterinarians to prevent or treat such infections in livestock. Its unlikely second act as an alleged pandemic cure-all dates back to April 2020, when Australian scientists reported that, in lab-cultured cells, ivermectin reduced the SARS-CoV-2 virus.
The fervor has grown ever since. “A near-perfect COVID prophylactic,” tweeted Bret Weinstein, a biologist who is best known for resigning from Evergreen State College in 2017 after he criticized an anti-racism education event. He has declared that the medication renders vaccines irrelevant. “If ivermectin, a drug out of patent, is safe and effective for treating and, more importantly, preventing COVID,” he told Fox News’ Tucker Carlson this summer, “then there shouldn’t be vaccines that we’re administering.”
Carvallo’s findings have been a powerful data point in this argument. The Front Line COVID-19 Critical Care Alliance (FLCCCA), a group of physicians that formed in March 2020, cites Carvallo’s study, along with others, in recommending that ivermectin be “systematically and globally adopted” as both a cure and preventative against COVID-19.
The head of the organization, pulmonologist Pierre Kory, talked up the study to Joe Rogan — the podcast star who said this week that he is now taking ivermectin, among other drugs, after testing positive for COVID. Kory also invoked it during a Senate committee hearing in December, when he asserted that ivermectin “basically obliterates transmission of this virus.”
“We just came across a trial last night from Argentina by the lead investigator of ivermectin in Argentina, Hector Carvallo,” Kory said. “They prophylaxed 800 healthcare workers. Not one got sick.” He didn’t return a request for comment.
Carvallo, who has written a handful of papers about ivermectin’s COVID-fighting potential over the last year, has publicly voiced his enthusiasm alongside Kory and other FLCCCA members. In the interview with BuzzFeed News, Carvallo compared ivermectin to penicillin and other drugs that were developed for one use and later found to be helpful for another. He called them “repurposed drugs,” saying that that’s a “bad word” in the scientific community.
Carvallo said that he and a colleague dove into ivermectin after COVID-19 hit Argentina in March 2020 and the government locked down virtually the entire country. “I closed my office when the pandemic broke out and dedicated myself to this kind of research,” he said.
Carvallo’s paper was based on two studies: a pilot, followed by an expanded run at multiple hospitals.
The timeline of these studies is unclear. According to a government-run clinical trials database, the initial study was conducted from June 1 to Aug. 10, 2020. The larger trial was done next, the paper reported. But the paper also said the second study took place from June 1 to Aug. 1. In the interview, Carvallo said the pilot was done from April to June and that the second study ended in August because the country’s health ministry had told him to stop. Why? “I wish I knew, but I don’t know,” he said. BuzzFeed News was unable to reach Argentina’s health ministry for comment.
In the pilot, reportedly conducted at Hospital Dr. A. Eurnekian near Buenos Aires’ international airport, a group of healthcare workers wore personal protective equipment and took the experimental therapy — a drop of ivermectin plus sprays of carrageenan, a seaweed extract and thickening agent — five times a day, every day, for two weeks. A comparison group only wore protective gear. A local Rotary Club donated $30,000 to purchase more PPE, Carvallo said, and the ivermectin and the carrageenan were donated by two drugmakers in Argentina.
BuzzFeed News was unable to reach one of the companies he cited, Laboratorios Panalab. But the other, Laboratorio Pablo Cassará, confirmed that it had provided both ivermectin and carrageenan to Carvallo’s study. According to company executive Roxana Pickenhayn, Carvallo had provided authorizations for his study; the main hospital where the research was done subsequently requested additional supplies. She noted that Cassará had also provided supplies for a copycat study in Argentina, which similarly found that the compounds were effective in preventing COVID.
The results reported by Carvallo’s team were striking. No one in the therapy group developed COVID over the two-week period or in the three weeks after that, whereas 11% of the control group tested positive, according to the paper.
Exactly how many people took part, though, is a source of confusion. The researchers wrote that 229 health personnel participated in the study, including 131 in the group taking ivermectin and carrageenan. But in an accompanying table, the numbers were slightly different: 231 total, with 132 taking ivermectin.
Meanwhile, the clinical trial database listing stated there were 229 participants. But other things didn’t add up. It said the control group had 72 women and 26 men, even though the paper had said 51 women and 48 men.
The ages also seemed mathematically improbable. The paper states that nearly 70% of participants taking the therapy were under age 40. Despite this, the clinical trial website states that the median age — the age at the midpoint of the group — was 42.
These might have been errors, Carvallo conceded in the interview, which was largely conducted in English. “We are not statistical people,” he said. He initially said that another researcher, Monica Lombardo, had reviewed the data, and “by passing from one hand to another, there may be a mistake.” But Lombardo, a nephrologist at CEMIC Hospital Universitario in Buenos Aires, told BuzzFeed News she was involved with neither the data collection nor analysis and played no role in the research. After being asked about this, Carvallo acknowledged that she was not involved.
In the next phase of trials, involving a total of 1,195 healthcare workers, the regimen was simplified (four doses of carrageenan a day, one 12-milligram dose of ivermectin a week), according to the paper, but the allegedly spectacular effect held steady: Zero people taking the therapy got COVID.
This, the paper reported, was true everywhere — whether among 600 healthcare workers at Hospital Dr. A. Eurnekian, 90 staffers at Hospital Municipal Ángel Marzetti, 90 workers at Hospital Cuenca Alta, or eight workers at Centro Médico Caseros. On the other hand, 58% of people in the control group got infected at a time when infections in Argentina were soaring.
Carvallo said that he, too, was surprised by this finding. “There’s no medicine that is 100% effective,” he said, but deferred to his statisticians who “found out that it was correct.” Other than Lombardo, who maintains she “had nothing to do with” the study, Carvallo did not cite any statisticians who had helped with his research.
His collaborator Roberto Hirsch, the chief of infectious diseases at Hospital Muñiz and a retired professor at the University of Buenos Aires’ medical school, also defended the results and said the study was conducted as advertised. “From our perspective, ivermectin is a complement to the vaccine and the new protocols that we've instituted, which starts with two months of weekly doses of ivermectin and then four months biweekly in order to impede the rate of transmission,” he said.
Carvallo said he tried to submit the article to prestigious journals before landing on the Journal of Biomedical Research and Clinical Investigation, which describes itself as “devoted to publishing the highest quality innovative papers in the field of Biomedical Research and Clinical Investigation.” It is a new periodical that, to date, has put out fewer than 10 articles since early 2019.
The journal’s website said it charges $1,950 to publish an article. After BuzzFeed News inquired about the fee, the figure posted on the site dropped to $1,200. According to Carvallo, he got some money from the two local drugmakers to cover the expense, and he and his colleagues paid the remainder out of pocket. Pickenhayn, the Cassará executive, said she did not know if the laboratory had provided financial support to Carvallo but added that the practice was common in Argentina.
The journal vetted the ivermectin paper in a week, publishing it on Nov. 17, 2020. A representative said Monday by email that “it was a fast peer-review process because of COVID-19.” They added, “We have taken all the measures to ensure there is no issue with our integrity.”
Earlier this summer, the paper’s inconsistencies caught the eye of Gideon Meyerowitz-Katz, an epidemiologist at the University of Wollongong in Australia. He’d already helped take apart one high-profile ivermectin study: a non-peer-reviewed preprint claiming that it cured COVID with 90% efficacy. After he and other data sleuths went public with concerns that its underlying data was fraudulent, that paper was taken down by its preprint server in July. (The FLCCCA, which had used the paper in part to recommend ivermectin, said that its removal “did not change the conclusion that ivermectin is highly effective in both prevention and treatment.”)
As Meyerowitz-Katz was tweeting his confusion about the Argentine paper, he encountered Sheldrick, who was asking similar questions.
“It’s one of the worst studies I’ve ever come across,” Meyerowitz-Katz told BuzzFeed News. He recalled wondering, Did this even happen?
For at least one hospital, the answer is no.
Once the paper started circulating, staffers at the Hospital Cuenca Alta, about an hour outside of Buenos Aires, grew alarmed. In December, its board of directors sent word to Argentina’s health ministry that it had no idea why it was listed as having participated.
“Although the aforementioned article contains data referring to patients from this [hospital] as participants in the respective clinical trial, they are false since this hospital did not participate in the investigation carried out,” a letter shared with BuzzFeed News read. The hospital’s ethics committee also did not receive any request to conduct the study.
Carvallo’s explanation is that the hospital wasn’t asked to participate as an institution. “It was not through ethics committees,” he said. Essentially, he claimed, staffers at local hospitals had heard about the pilot study’s promising results through word of mouth and individually wanted to participate at a time when no COVID vaccines were available.
But if those hospitals did not formally help administer the study, how, then, did Carvallo ensure that hundreds of volunteers correctly self-administered the ivermectin and carrageenan doses multiple times per day or week for months? His answer: the honor system.
“We had to trust them,” he said.
Hospital Dr. A. Eurnekian, where Carvallo has practiced, did green-light the study, according to a letter from its ethics committee that he provided.
But phone calls and emails to the medical director at one of the other hospitals named in the paper, Hospital Municipal Ángel Marzetti, were not returned. No valid contact information could be found for a fourth hospital, Centro Médico Caseros, which appears to have no website or working phone.
Javier Farina, an infectious diseases doctor at Hospital Cuenca Alta and a member of its ethics committee, acknowledged that staff members may have individually participated and noted that it is common in Argentina for employees to work at different hospitals. But as far as he knew, he said in a text message, “None of my colleagues participated [in] this trial.” And he hadn’t heard of Carvallo sending around any ads looking for volunteers.
“Carvallo never contacted our authorities to [include] our center in his trial,” he wrote.
Farina and his staff also complained to the Journal of Biomedical Research and Clinical Investigation. All mentions of Hospital Cuenca Alta on the web version of the paper were recently replaced with “Other peripheral Medical Centre,” with no acknowledgment of these changes.
Carvallo said the institution’s name was removed because it later undertook a study about another type of treatment. “They say that as a hospital they couldn’t participate in any other trial,” he said. Farina denied this, saying Carvallo’s explanation was “an absolut[e] lie.”
The Hospital Cuenca Alta doctors were not the only ones concerned enough to complain. When early results started circulating online, members of the health ministry of Buenos Aires province told national research ethics officials that that study — plus another, separate study of Carvallo’s about ivermectin as a COVID-19 treatment — did not have approval from any accredited ethics committee or local health officials in that province, according to correspondence seen by BuzzFeed News. The paper stated that “ethics board approval was attained prior to the commencement of this study and all participants provided informed consent prior to study enrollment.”
When other scientists — including one of Carvallo’s own collaborators — tried to get answers, they say they were kept in the dark.
A little over a month ago, Sheldrick, one of the data sleuths, posed his questions to Carvallo over email. He also requested an anonymized version of his team’s underlying data. Carvallo was unaccommodating. “You will find all the details in the attached peer-reviewed article,” he wrote on July 27 in an exchange shared with BuzzFeed News.
Sheldrick pushed back, this time adding two of his coauthors to the email chain, but Carvallo stood firm. He also did not concede that there were problems. “For all discrepancies in data treatment (if there are any) I and the staticians [sic] that worked with me are responsible,” he responded on Aug. 1.
He did pledge to release the data “when the pandemic is over.”
But that was too long a wait for his coauthor Alkis Psaltis, a head and neck surgeon at the Queen Elizabeth Hospital near Adelaide, Australia.
“I don’t have the data but would have no objections to the raw data being released to you provided it’s anonymised,” he replied to Sheldrick and the group.
“I would actually like to see the raw data released also for my own confidence in this study’s claims. Please oblige Hector,” he wrote, addressing Carvallo.
Carvallo told BuzzFeed News that he gave Psaltis the data. But according to emails that Psaltis provided, Carvallo only sent him summaries of the results and a written narrative of how the study was carried out.
“You have not provided me with any RAW DATA as I requested,” Psaltis responded to Carvallo on Aug. 22.
He continued, “Without seeing the data I cannot be satisfied that it is accurate, particularly given the concerns that have been raised by multiple independent people. For this reason, I am requesting to be removed from the manuscript and I will write to the journal to ask for this to happen.” Psaltis’s name was taken off shortly thereafter.
Both Carvallo and Hirsch said that Psaltis was named as a coauthor only as a “courtesy.” Since he never actually saw any of the subjects, they added, he didn’t need to see the underlying data.
When BuzzFeed News asked to see the raw data, Carvallo sent a spreadsheet that was not for the study in question, but rather what he said was a different study about ivermectin.
Psaltis told BuzzFeed News he does not know Carvallo personally and that they were introduced by a mutual colleague. He was invited to participate, he said, because he had previously used carrageenan to treat sinus bacterial infections. Tasked with reading the carrageenan section of the study, he believed that they would submit the article to the Medical Journal of Australia.
By the time he got involved, the data collection and initial write-up were done, Psaltis said. He corrected grammar, made structural changes, and suggested additional information that he’d like to see — recommendations that, according to him, were mostly ignored. Carvallo told him that he “accepted the limitations of the article,” but was eager to submit it because he thought the protocol could help save lives, Psaltis said by email.
The next update, according to Psaltis, came when Carvallo informed him that it had been published in the Journal of Biomedical Research and Clinical Investigation, which he’d never heard of.
In retrospect, Psaltis said, being caught up in an all-hands-on-deck health emergency may have led him to be too credulous. “I trusted the information provided to me by desperate medical colleagues in the hope that health care workers could be given some degree of protection against this largely unknown virus,” Psaltis wrote.
It isn’t the first time during the pandemic that researchers have avoided sharing data that turned out to be suspect. In May 2020, scientists and journalists noted inconsistencies in an influential paper reporting that hydroxychloroquine was fatally dangerous for COVID patients. When called to release the data, provided by a company called Surgisphere, most of the authors admitted that they had never seen it and that their collaborator and Surgisphere’s founder, Sapan Desai, had refused to hand it over. That led to the paper’s retraction.
Now, the questions around the Argentine ivermectin study raise more doubts about whether the drug can prevent COVID.
“It looks really bad for the people who have been promoting ivermectin uncritically,” Meyerowitz-Katz said.
But in Carvallo’s telling, at least, it is only a matter of time before the world sees in ivermectin what he sees.
“All truth passes through three phases,” he said. “First it is ridiculed, then it is violently opposed, then it is accepted as self-evident. We are in phase two now.” ●
This story has been updated with a comment from the Journal of Biomedical Research and Clinical Investigation about why it reinstated the study after taking it down.
Correction: America's Frontline Doctors touted hydroxychloroquine at a press conference on the steps of the US Supreme Court. The location was misidentified in an earlier version of this story.