and vaccine-induced immunity. can you explain what that means and is it possible the omicron variant is what scientists like you call an escape variant? >> it's possible, but again, based on what we've learned so far with alpha, beta, gamma and delta, the vaccines which are generated against the original virus hill work and the boosters work particularly well. this is an important point, where people are listening who haven't gotten boosted but did get their original vaccine and eligible, this is another reason to do that now. the booster enlarges the capacity of your immune system to recognize all kinds of different spike proteins it's never seen. this is a great day to get boosted or find out how to do so at vaccines.gov. but yes, we worry in the worst case you might have a virus that is so different that the vaccines really don't enable you to have protection. that's the kind of thing we need to check out as quickly as possible.