Director of the National Institute of Allergy and Infectious Diseases Anthony Fauci speaks during the daily briefing on the novel coronavirus, COVID-19, in the Brady Briefing Room at the White House on April 1, 2020, in Washington, DC.

President Donald Trump has said chloroquine and hydroxychloroquine could be a "game-changer," even though the drugs have not been put through rigorous clinical trials to fight CV-19, which has infected more than 1 million people worldwide in a little over three months. Trump last month directed the FDA to examine whether the drugs can be used to prevent or treat the coronavirus.

New York state last week began the first large-scale clinical trial looking at hydroxychloroquine as a possible treatment for the coronavirus after the Food and Drug Administration fast-tracked the approval process.

"We still need to do the definitive studies to determine whether any intervention, not just this one, is truly safe and effective," Fauci, the director of the National Institute of Allergy and Infectious Diseases, said on Fox News. "But when you don't have that information, it's understandable why people might want to take something anyway even with the slightest hint of being effective."

The drug, a derivative of anti-malaria drug chloroquine, has been proven to help people with rheumatoid arthritis and lupus. Fauci said Friday that he worries that the hype for treating the coronavirus will spur a shortage of the drug for those who need it for a "proven indication."

That being said, doctors can give the drug to patients in a common and legal practice known as "off-label" prescribing, Fauci said. "Off label" means the drug is being used for an ailment not yet approved by the FDA.

Fauci said the only tool we have right now for fighting the coronavirus is social distancing, urging Americans to follow guidelines from U.S. health officials on staying indoors.

He said health officials are also watching for the number of new cases or deaths to decline, indicating that the outbreak is abating. A decreasing number of deaths is the best indicator that the outbreak is slowing, he said.

"The deaths generally lag behind the other aspects of it. You could see an improvement in the less number of cases per day and at the same time see an increase in deaths," he said. "When you start seeing a decrease in deaths, that's very good news."

As the public waits for a treatment, U.S. officials are also working on a vaccine to prevent the infection.

On Wednesday, Fauci said the first human trial testing a potential vaccine to prevent COVID-19 is "on track," with public distribution still projected in 12 to 18 months, which would be the "ultimate game changer" in the fight against the pandemic.