Fact check: Claim that ivermectin causes male sterility is based on deeply flawed study

McKenzie Sadeghi, USA TODAY
·6 min read

The claim: Ivermectin causes sterilization in 85% of men

Many vaccine opponents have touted unproven cures for COVID-19 such as ivermectin, an anti-parasitic drug health officials warn can result in dangerous symptoms, including nausea, diarrhea, low blood pressure and even death.

But online, some people claim there is another side effect of the drug that people should be concerned about: male infertility.

“Ivermectin causes sterilization in 85 percent of men, study finds,” reads the headline of an article, which was shared as a screenshot to Facebook on Sept. 9. The post accumulated more than 1,200 reactions within less than a week.

Throughout that week, similar versions of the claim made their way to Instagram, Twitter, Reddit and news reports. On Sept. 7, there was a spike in searches for "ivermectin infertility," according to Google Trends data.

The screenshot showed a Sept. 8 article from KTSM-TV in El Paso, Texas, which was taken down the next day. A note left in its place said it was removed due to "concerns over the scientific research methods, the veracity of the original, peer-reviewed report and public statements by the Food and Drug Administration (FDA) saying that infertility is not a known side effect of Ivermectin."

Indeed, the claim that ivermectin causes infertility in men is based on one study conducted more than a decade ago that used flawed methodologies and was published in a questionable journal, according to experts who spoke with USA TODAY.

Fact check: Pfizer, Moderna and Johnson & Johnson COVID-19 vaccines all passed animal testing

The social media users did not respond to a request for comment.

Flawed 2011 study

The claim that ivermectin causes infertility traces back to a flawed 2011 Nigerian study, in which researchers analyzed 37 men with onchocerciasis. The illness, also known as river blindness, was caused by a parasitic worm and treated with ivermectin.

Notably, the study itself, does not actually include the 85% figure. The 2011 study claims that number came from a separate 2002 report from the Journal of Biomedical Investigation and lists it in the references. USA TODAY could not locate the 2002 paper online.

In any case, experts say the Nigerian study supports no such conclusion.

The study, titled, “Effects of Ivermectin therapy on the sperm functions of Nigerian onchocerciasis patients,” appears in the Scholars Research Library in the Journal Archives of Applied Science Research, which has had its Twitter account suspended.

Per IFL Science, the journal "bears some hallmarks of a 'predatory journal,'" which will publish anything that is submitted for a fee and makes it easier to get around the reviewing process. Because these sites don't rely on a paywall for income, they typically ask researchers to pay a publication fee.

After studying the 37 men who were treated with ivermectin for 11 months, researchers of the study concluded there was a “significant reduction in the sperm counts and sperm motility of the patients tested.”

However, Dr. Amin Herati, a urologist and the director of Male Infertility and Men’s Health at Johns Hopkins Medicine, said a reduction in concentration, motility and morphology does not always translate to lower fertility potential or sterilization.

"The study from 2011 has many limitations that make the results extremely difficult to generalize to other patients taking ivermectin," Herati said via email. "The absence of a control group is a significant one since the inflammatory response to the parasitic infection could put stress on the reproductive system, causing impaired semen parameters."

To generalize the results, Herati said more study would need to be done that was in line with the World Health Organization Laboratory Manual guidelines for examining and processing sperm. Those guidelines weren't followed in the Nigerian study.

Dr. Michael Eisenberg, the director of Male Reproductive Medicine and Surgery at Stanford University, said while the intent of the study is "laudable," the results don't support the 85% claim.

"The WHO publishes a reference range for semen quality to determine what is average semen quality and what numbers are adequate for pregnancy," Eisenberg said. "Based on those numbers, very few men had any clinically significant changes in their semen quality after treatment in any parameter."

Gideon Meyerowitz-Katz, an epidemiologist at Australia’s University of Wollongong, highlighted other issues with the study in a Twitter thread, such as how 90% of participants were excluded from the study prior to taking ivermectin due to low sperm count.

USA TODAY reached out to authors of the study, the Scholars Research Library and the Journal Archives of Applied Science Research for additional comment.

Fact check: There is no evidence 45,000 people died from vaccine-related complications

FDA on ivermectin

Infertility in men is not listed as a side effect in the labeling of ivermectin, which states that the drug had no adverse effects on fertility in rats in studies at repeated doses of up to three times the maximum recommended human dose, according to Chanapa Tantibanchachai, a spokesperson for the U.S. Food and Drug Administration.

"However, The FDA continues to monitor reports of all adverse events with ivermectin and will update the public as more information becomes available," Tantibanchachai said via email.

The Food and Drug Administration and the National Institutes of Health COVID-19 Treatment Guidelines Panel say ivermectin is not an authorized or approved treatment for preventing or treating COVID-19.

USA TODAY has previously debunked claims that ivermectin is an effective treatment for the virus.

Fact check: Sugar substitute xylitol is dangerous for dogs, found in sugar-free foods

Our rating: False

Based on our research, we rate FALSE the claim that ivermectin causes sterilization in 85% of men. The claim is based on a 2011 Nigerian study, which had no control group, a small sample size and other methodological issues. Experts told USA TODAY the study should not be used to make a generalized conclusion, and the parasitic illness being treated with ivermectin could have contributed to the changes in semen quality.

Our fact-check sources:

Thank you for supporting our journalism. You can subscribe to our print edition, ad-free app, or electronic newspaper replica here.

Our fact-check work is supported in part by a grant from Facebook.

This article originally appeared on USA TODAY: Fact check: False claim that ivermectin causes sterility in 85% of men