Does the US have to wear masks again for the Delta variant of Covid?

New CDC guidance and breakthrough infections have sown confusion. Here's some sound advice from two epidemiologists on how to keep safe

In late July, the US Centers for Disease Control and Prevention reversed its earlier mask-wearing guidance for people vaccinated against Covid-19 by recommending that even those who are fully vaccinated resume masking indoors, in public, if they live in areas with substantial or high transmission" of the virus. The update was a jarring 180 from the previous CDC mask guidance issued in May, which gave fully vaccinated individuals the green light to remove face coverings and resume activities without social distancing.

Confusing? Maybe just a bit. But there's a logic to the CDC's about-face.