Hydroxychloroquine, the drug U.S. President Donald Trump took to prevent COVID-19 against the advice from the U.S. Food and Drug Administration, failed to prevent infection in a new study.
In the new research, published in The New England Journal of Medicine, people at risk of infection who took hydroxychloroquine were no less likely to develop COVID-19, the disease caused by the coronavirus, than people taking a sugar pill.
"We were a little bit disappointed that obviously it didn't work," said study lead David Boulware of the University of Minnesota.
Other studies have suggested that the drug does not help treat patients already sick with COVID-19, either, though questions surround those studies.
Doctors had hoped that hydroxychloroquine, a cheap and widely available drug for malaria, lupus and rheumatoid arthritis, might work against the coronavirus based on test tube studies. Small, early studies also seemed to show the drug helped treat sick COVID-19 patients.
But other scientists questioned those results and urged caution. The publisher of one of the most influential early reports has since said the study does not meet its standards.
With nothing else available to help COVID-19 patients, "many thousands of people were treated with it in the hope that it would do some good but in the absence of any really valid evidence that it worked," Johns Hopkins University epidemiologist Richard Chaisson said.
Chaisson was not involved in the prevention study, but he is leading separate research on hydroxychloroquine to treat hospitalized COVID-19 patients.
The new prevention trial involved about 800 people who had been exposed to someone with a laboratory-confirmed case of COVID-19.
Two-thirds were health care workers. The others were caring for infected family members. Half of the participants received hydroxychloroquine. Half received a placebo.
Two weeks after exposure, there wasn't much difference between the two. About 12% of those taking hydroxychloroquine developed COVID-19, compared to about 14% of those taking a placebo.
"It would be great to have a preventive therapy," Boulware said. "Based on our trial, we would say that hydroxychloroquine is not the medicine that's going to do that."
About 40% of patients taking hydroxychloroquine had nausea, upset stomachs, diarrhea or other negative reactions.
None had serious side effects. Patients in some other studies developed heart problems, leading the FDA to caution against its use for COVID-19 outside clinical trials.
"One unfortunate thing that has happened here is there has been a lot of hype about this drug," and it's getting in the way of good science, Chaisson said.
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Trump has been advocating for it since March. Last month he said he was taking the drug after his personal valet tested positive for the coronavirus. Popular conservative media commentator Laura Ingraham has called hydroxychloroquine a "game changer."
A recent study found that the drug did not help treat COVID-19 patients and may have done harm.
But it was not designed to provide definitive answers. And after criticism from other scientists about the data, the publisher issued an "expression of concern" and commissioned an audit of the research.
That means it's still not settled whether hydroxychloroquine helps treat COVID-19.
On the other hand, the new study provides strong evidence that it does not prevent infection.
"This is the first really well-done comparative study," said Harvard Medical School infectious-disease physician Raj Gandhi, who helped write the Infectious Diseases Society of America's COVID-19 treatment guidelines for physicians.
But there's more work to do, he added.
"The message shouldn't be that the studies for treatment should stop," he said. "You're actually obligated to do a study because otherwise you will never know an answer. And we really need to know an answer."