How Can You Tell If A COVID-19 Vaccine Is Working?
Several COVID-19 vaccine candidates are being tested now. But why does it take 30,000 volunteers to know if one is safe and effective? And what does it mean to say a vaccine candidate is working?
Several vaccines are currently in large-scale studies to see if they can prevent COVID-19, and more are on the way.
President Trump has been hinting that a vaccine could be ready before the end of October, but Moncef Slaoui, chief scientific adviser to the administration's Operation Warp Speed, downplayed that possibility in an interview on NPR's All Things Considered.
"There is a very,
