one is someone who halls had covid, do they have more or less immunity than somebody who has a vaccine but didn't have covid? >> that's a really important question and one that is being actively scientifically followed. we do know that people who have infection induced immunity get a robust response. some of them do. we have seen data that has demonstrated that we have also seen data that if you vaccinate both people they're two and a half times more protected than they would have been if you don't vaccinate those people. and that's the reason for the recommendation vaccinate people who have infection induced immunity. importantly though, there are things we don't know. so we don't know, for example, what if you only had mild disease? or what if you had disease months ago and how much has your immunity waned or, in fact, what if you had a different variant? how well is your protection against delta variant if you have had alpha or wild type