>> and, tom, back to the boosters for teens. there is not complete agreement among doctors about the need for them. >> not at all, including dr. paul offit on the fda's advisory panel for vaccines he doesn't think teenagers need boosters he doesn't think they will get that sick right now from covid or the mutations he's more concerned about heart inflammation with teenage boys than he is really about covid. but, again, we have full approval now from the fda and the cdc, lester. >> tom costello, thank you. we're tracking the first big winter storm of the season sweeping across the country winter weather alerts are up across 17 states from the west coast to the great lakes. up to three feet of snow forecast in some areas. by the start of the weekend, it is expected to bring severe weather to the southeast and mid-atlantic i want to turn now to the crisis in ukraine with fears of a potential russian invasion president biden holding another high stakes call. this time with ukraine's president. kristin welker is at the white house. what do we know about today's call, kristin?