Asked about how possible herd immunity could help the US move past the coronavirus pandemic, Dr. Anthony Fauci noted there's still "a lot we don’t know" about immunity — including how long it lasts.
"What we don’t know is what the durability is," he said at an ongoing Senate hearing. “So if you wind up getting herd immunity to 75, 80%, what we need to learn, and only time will teach us this, is how long does immunity last? Is it a year? Two, three, four? Or is it less?”
Fauci said the immunity durability — or how long it protects a person — could affect how often a possible coronavirus vaccine needs updating.
Dr. Robert Redfield, the director of the US Centers for Disease Control and Prevention, also noted that as of now, only about 5% to 8% of the American public has “experienced this virus," underscoring the need for a vaccine.