moderna's, you can get a pfizer booster. who is this good news for, doctor? >> so in particular, people who got johnson & johnson. we've known for some time now for at least a few months that this was going to be a two-dose vaccine, a two-dose regimen would be needed. it's not to say that johnson & johnson vaccine is inferior. after all, we give two doses of the pfizer and moderna and are now for certain groups giving a third dose. but i think in particular for people who got the johnson & johnson vaccine, getting some guidance as to what second dose should be given, it does appear that they may benefit, that group in particular may benefit from mixing and matching. so if they got the johnson & johnson first, to get either pfizer or moderna second does seem to be the more advisable course here. >> speaking of the fda, former director scott gottlieb tweeted this on sunday. uk reported its biggest one-day case increase in three months, just as this new delta variant