should we therefore be expecting to see another wave like we saw with delta? you see this kind of consistent pattern here, kind of burns out a little bit, then a new variant, delta comes up, then it burns out and now you have omicron. is that the path of this that folks should be preparing for? >> i think so. again, i would be very cautious in making statements about how transmissible this new variant is. you need a lot of data to be able to make that statement confidently. it's a little too early to tell. yes, of course, there are various discussions about why we're seeing these variants come and go, but i think the major driver is our own immune system, in particular, our neutralizing antibodies. as we mount against them, the variants tend to escape them.