A top vaccine expert says the idea the U.S. could wait for the coronavirus to burn out through herd immunity is ‘fanciful, it's never happened before with any virus, and it's not going to happen with this virus.’ @DrPaulOffit discusses @PamelaBrownCNN pic.twitter.com/3oS8KGb9El— The Lead CNN (@TheLeadCNN) August 31, 2020