surge in cases. the cdc says it will not change the definition of what it means to be fully vaccinated. but the agency released new guidance today and now recommending that all people, all eligible people stay quote, up to date. staying up today with covid vaccine shots. back with us tonight is celine gounder, professor of menace and infectious diseases at the end why you school of medicine and bellevue hospital. she is part of a panel that advised the biden team. she hosts a weekly podcast on the impact of the coronavirus called epidemic. doctor gounder, it is good to see you again. i want to get your sense of this. because you and i have been talking throughout the entire pandemic about the pattern of it. when we saw omicron start in south africa we saw a steep ramp up and then we saw a steep dropoff. and we saw that elsewhere. americas bigger. the geography is larger. it is more complicated. how do you process where we are in this continued moment and how we should be responding? >> ali, i do think that we are