No Evidence Hydroxychloroquine Is Helpful In Preventing COVID-19, Study Finds

Jun 3, 2020
Originally published on June 11, 2020 2:13 pm

Taking hydroxychloroquine after being exposed to someone with COVID-19 does not protect someone from getting the disease.

That's the conclusion of a study published Wednesday involving 821 participants. All had direct exposure to a COVID-19 patient, either because they lived with one, or were a health care provider or first responder.

The study had an unusual design. "It was all web-based," says Radha Rajasingham, an infectious disease physician at the University of Minnesota. "People would go to our website if they were interested in enrolling."

To qualify, people had to be within a few days of their encounter with a COVID-19 patient and not have any symptoms of the disease themselves. Encounters meant being within 6 feet of a sick person for more than 10 minutes while wearing neither a face mask nor an eye shield or while wearing a face mask but no face shield. The volunteers received either a five-day supply of hydroxychloroquine, or a placebo.

As Rajasingham and her colleagues report in the New England Journal of Medicine, 107 of the 821 participants developed disease; 49 in the group receiving hydroxychloroquine and 58 in the placebo group. That turned out to be an absolute risk reduction in risk of 2.4%. That difference was not statistically significant, and "it's also not clinically meaningful," Rajasingham says. She would like to have seen a relative risk reduction of 30% or more before recommending hydroxychloroquine to asymptomatic patients. She says hydroxychloroquine can have serious side effects, although the side effects reported in this study were relatively mild.

The prevention study was dreamed up by David Boulware at the University of Minnesota. "This is not my day job," he says. "My normal research is doing clinical trials in Africa for fungal meningitis of the brain."

He remembers thinking somebody needed to do something to help fight the COVID-19 pandemic, and the he realized, "I think that's us."

So he got his team together, and they put together this study of hydroxychloroquine. "Within eight days, we basically had the trial up and running," including all the necessary regulatory approvals." Remarkably, fewer than three months from the day was conceived, he had a paper in a prestigious medical journal.

Researchers have been interested in the possibility of using hydroxychloroquine to prevent or treat COVID-19 because it seems to impair the virus' ability to infect cells in the lab. The drug's effectiveness in treating hospitalized patients is still an open question, but if there is a benefit, it is most likely a small one.

Now it appears the drug is not effective at preventing disease in people who have been exposed with minimal or no protection. It remains an open question whether it might be effective in preventing the disease in people who have used appropriate protective gear to prevent exposure. There is currently a multi-center study underway intended to enroll 15,000 people to answer that question.

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The drug hydroxychloroquine has been getting a lot of attention, not least because President Trump said he was taking it. This drug inhibits the coronavirus in cells in the lab, and so there was hope it might do the same in people. Well, now a scientific study with more than 800 participants has failed to show the drug has any benefit for preventing COVID-19 infection. Here's NPR's Joe Palca.

JOE PALCA, BYLINE: Much of the debate about hydroxychloroquine has swirled around whether the drug was any good for treating patients hospitalized with COVID-19. But Dr. Radha Rajasingham and her colleagues at the University of Minnesota wanted to ask a different question. Could hydroxychloroquine prevent disease in someone who had been exposed to COVID-19 but wasn't yet sick? So they divided 821 people who'd been exposed into two groups - one got a five-day course of the drug, and the other a placebo - and looked to see how many in each group came down with the disease. They did see a reduction in the group taking the drug, but it was extremely modest.

RADHA RAJASINGHAM: So the absolute risk reduction in this study was 2.4%.

PALCA: And not only was it modest, it was not statistically significant.

RAJASINGHAM: Even if it was statistically significant, which it was not, we do have to think about what is meaningful clinically.

PALCA: Rajasingham says a 2.4% risk reduction probably isn't worth the risk of side effects.

RAJASINGHAM: About 40% of people reported side effects. They were mild side effects.

PALCA: But there are more serious side effects, including heart problems, known to be associated with hydroxychloroquine. Rajasingham's study appears in the New England Journal of Medicine. There's another, much larger study of hydroxychloroquine underway for preventing COVID-19. Mario Castro is a pulmonologist at the University of Kansas and an investigator in that study, known by the acronym HERO. He says HERO differs from the Rajasingham study in three ways. First, it only looks at health care workers exposed to COVID-19 patients.

MARIO CASTRO: The second is the treatment in HERO is for 30 days.

PALCA: And the third is it uses a lower dose of the drug. Castro says even a small benefit, like the one Rajasingham's study found, might be valuable if they find it.

CASTRO: It's like everything we do in medicine. It's all balancing the benefits and the potential risks.

PALCA: The HERO study should provide more information about just how big those risks and benefits are.

Joe Palca, NPR News.

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