contract covid and get higher doses. and the potential gender differences there. but also the way that this virus seems to enter the body is through a receptor known as the ace 2 receptor. it's sort of a lock and key mechanism. and men in certain areas of the body, including the lungs and gi tract, may have more of these receptors as well. these are some of the areas that i think investigators are still looking. as we've had more treatments for covid, the disparity in gender in terms of severe illness and death has gone down. let's switch gears to a remarkable medical breakthrough. for the first time, surgeons in new york were able to transplant a pig kidney to a human without immediate rejection. how big a deal is this? >> this is potentially a big deal, jake. there are a lot of people who are waiting for kidney transplants. and there aren't enough donors.