When will the U.S. reach herd immunity? What about California? Or the world? We asked four doctors to define herd immunity and estimate when we might get there with COVID-19. Herd immunity went from a ...

It's almost amusing to think of humans as part of a "herd" — a term that usually conjures up images of hoofed animals grazing in a field. Yet herd immunity is an important concept when it comes to ...

As more and more of the United States population gets vaccinated against COVID-19, many are wondering: when will enough people be vaccinated for life to return to normal? That question doesn't have a ...

Herd immunity went from a phrase most of us had never heard of to the thing we're all waiting for in just about a year's time. "It's kind of shorthand for back to normal," said Dr. Bob Wachter, chair ...