How do you know when an experimental drug is working? For scientists, that answer only comes from carefully controlled clinical trials.
For President Trump, such trials aren't something he wants to wait on before promoting such a drug.
At Tuesday's White House coronavirus task force briefing, Trump told the story of a woman from Michigan who was sick with COVID-19 — a story he had seen on television the night before.
"She was just in horrible shape for 12 days, 14 days," Trump said. "She thought she was dead." The president said she implored her husband to obtain hydroxychloroquine, and the husband did so.
"Four hours later, she awoke and she said, I feel better," Trump recalled. "And then, shortly thereafter, she felt great."
"The way she spoke," Trump said, "it was like a miracle. And this was not a fan of mine, but she's a fan of my now."
To be clear, the president acknowledged that it doesn't always turn out this way. But waiting for scientific evidence that a drug is effective is not something the president was eager to do.
"We got people dying in this country and all over the world right now, not in a couple of years," he said.
Relying on such anecdotal evidence can be misleading. And the drug Trump is promoting can have serious side effects.
Let's start with the story: Trump says the woman had been ill for "12 days, 14 days." According to the Centers for Disease Control and Prevention, the median length of hospitalization among survivors is 10 to 13 days.
That means the woman was at a point in the disease where most people — even people sick enough to be hospitalized — get better. In other words, the woman Trump described might have gotten better without any drug. It's impossible to say without controlled clinical trials.
Although this woman didn't get worse after taking the drug, some people might. Without controlled clinical trials, it's not possible to know. Another question: Would the woman have gotten better, or worse, if she had taken the drug earlier in the course of her disease?
Without proper studies, it's an unknown.
Clinical trials do take time, but with so many people sick, it might be possible to reduce the time it takes to complete a clinical trial to months or even weeks.
When people are desperate, they might be ready to try anything. The Food and Drug Administration was created in part to protect people from false claims. Some people get frustrated with the FDA because it takes so long to approve drugs, but the agency makes its decision about whether a drug works — and is safe — based on data.