Omicron has reached the U.S., and widespread vaccination may not be enough to keep the new variant from spreading. The variant is expected to outpace Delta in the coming weeks, with more than 30 states having now reported a case.On this week's episode, Abraar Karan, MD, MPH, an infectious disease physician at Stanford University, joins us to explain all we know -- and still don't -- when it comes to this new variant.