Americans shouldn’t assume hydroxychloroquine is a “knockout drug” in preventing or treating COVID-19, White House health advisor Dr. Anthony Fauci warned Friday. “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.”