It's a whiplash kind of day in this pandemic.

The U.S. passed 300,000 dead. Boston, Somerville, Newton, Brockton and Winthrop prepare for a modified rollback. At the same time, Phase One of vaccinations started in earnest today, and the federal Food and Drug Administration is moving forward on emergency authorization for a second vaccine.

We take listener questions and make sense of it all with Dr. Shira Doron, an infectious disease physician and hospital epidemiologist at Tufts Medical Center, and Dr. Benjamin Linas, an infectious disease physician at Boston Medical Center.