Reconsidering Ivermectin

 by David R Henderson

Natural immunity from repeated infections, the development of vaccines against the virus SARS-CoV‑2, and antivirals to treat infection have dramatically reduced serious illness and death from COVID-19. Still, COVID remains a meaningful cause of illness and death around the world. Even in the United States, COVID now kills about 20,000 a year. For that reason, it is helpful to look for cheap, widely available medicines as additional treatments.

While the COVID pandemic was raging, we wrote in Regulation that the antiparasitic drug ivermectin showed promise as a treatment and preventative. In Hooper and Henderson (2022a), we disagreed with researchers who dismissed it because studies showed “only” 93 percent confidence that it was effective. In Hooper and Henderson (2022b), we argued that, contrary to the reported results of a major trial of the drug that was conducted in Brazil known as the TOGETHER Trial, the data suggested it was effective for many who were in the trial.

In science, of course, no one ever gets the last word. Controversies are ongoing. A prominent analysis of ivermectin by the highly reputable Cochrane Library, Popp et al. (2026), claims that the consensus of the academic literature is that ivermectin was ineffective against COVID. This conclusion is faulty. As we document below, Popp et al. were too selective on which studies to include in their analysis, and several of those studies were of poor quality. Instead of upholding Cochrane’s reputation for quality and, therefore, being the last word on ivermectin, this analysis is, unfortunately, unreliable.

These are the opening 3 paragraphs of Charley Hooper’s and my latest. It’s Charles L. Hooper and David R. Henderson, “Reconsidering Ivermectin,” Regulation, Spring 2026.

And:

A second meta-analysis, Song et al. (2024), reported, “There was no significant difference in all-cause mortality rate between [ivermectin] and controls.” And yet 62.7 percent of the mortality results used to develop that conclusion came from one of the Knackered Nine, Elshafie et al. (2022). The next highest mortality share, 12.6 percent, came from Rezai et al. (2022), another of the Knackered Nine. The most serious and damning complication was that one of that study’s researchers, Andrew Hill, was recorded on video admitting that the conclusions of his ivermectin research were not based on the data but were requested by a funding organization.

Our conclusion:

If we average the mortality benefit of ivermectin in the nine meta-analyses (including the three that claimed no benefit), we calculate a 47 percent reduction in mortality when the drug is used. If that is roughly accurate, it would mean that ivermectin had the potential to reduce the death toll from COVID-19 during the worst years of the disease by nearly half. Millions could have lived. Even today, in the United States where COVID kills about 20,000 a year, wider use of ivermectin could help to save lives.

In short, the Popp et al. Cochrane report on ivermectin was too selective on which data to include and a large percentage of the data that it did use was of poor quality. That’s not the way to make a good hamburger or a good meta-analysis.

Read the whole thing.

https://davidrhenderson.substack.com/p/reconsidering-ivermectin