On Monday, President Donald Trump said he has been taking hydroxychloroquine to prevent COVID-19, the illness caused by the new coronavirus.

Hydroxychloroquine, an old malaria drug that is also used for the treatment of rheumatoid arthritis and lupus, is an unproven drug for COVID-19, which has vigorously been promoted by the president.

Trump said at the White House, “A lot of good things have come out about the hydroxy. A lot of good things have come out. You’d be surprised at how many people are taking it, especially the front-line workers — before you catch it. I happen to be taking it. I happen to be taking it. … I’m taking it — hydroxychloroquine — right now.”

The president said he does not believe he was exposed to the virus; however, he decided to take hydroxychloroquine after consulting with the White House physician.

Trump also claimed that essential health workers, including doctors and nurses, have been taking the drug to prevent the illness caused by the coronavirus.

Dr. Sean Conley, the incumbent physician to the president, said that he discussed the drug with Trump.

Dr. Conley, who is the White House physician, said, “After numerous discussions, he and I had for and against the use of hydroxychloroquine we concluded the potential benefit from treatment outweighed the relative risks.”

Dr. Conley said Trump receives regular coronavirus testing and continues to test negative.

According to one White House official, Trump started taking hydroxychloroquine after his valet tested positive for COVID-19 earlier this month. The president said at the time he had “a very little contact” with the valet.

The White House official said only a few people of aides knew that Trump was taking the drug.

Vice President Mike Pence’s office did not respond to questions if he is also taking hydroxychloroquine to prevent COVID-19. His press secretary, Katie Miller, tested positive for COVID-19 earlier this month.

The U.S. Food and Drug Administration (FDA) has warned against using hydroxychloroquine for COVID-19 outside of hospital settings because the drug carries a risk of serious heart problems.

Trump was asked why he was using an unproven drug to prevent COVID-19. He replied, “Because I think it’s good. I’ve heard a lot of good stories. I’m not going to get hurt by it. It’s been around for 40 years.”

However, Trump dismissed questions about studies that have shown that the drug was not effective at treating COVID-19. He said he received a “well-crafted” letter from a doctor in Westchester, New York, who claimed to have treated patients with a combination of hydroxychloroquine, zinc, and azithromycin (antibiotic).

Trump went on to say he was also taking zinc and he seemed to suggest that he had also previously taken azithromycin.

The president repeatedly said front-line health workers were taking hydroxychloroquine, even though some experts have warned against the use of the drug.

In April, the American Medical Association (AMA), the American Pharmacists Association (APA), and the American Society of Health-System Pharmacists released a joint statement “that some physicians and others are prophylactically prescribing medications currently identified as potential treatments for COVID-19.”

They added, “We strongly oppose these actions. We caution hospitals, health systems, and individual practitioners that no medication has been FDA-approved for use in COVID-19 patients.”

Trump was asked to show evidence of the drug’s efficacy at treating COVID-19. He said. “Here’s my evidence. I get a lot of positive calls about it.” However, experts have said there is no strong evidence to prove that hydroxychloroquine treats COVID-19.