in addition to those circulating antibodies which may be dropping off, the memory b cells and t cells are able to give you more durability in your immune response. so you see a different interpretation of when the booster should be given. i think it is closer to the five-month mark. we are looking at six months out from the completed series in the u.s. that is all open to further discovery and further change in the policy. >> dr. purnell, we're all looking for signs or clues whether omicron is different than previous variants. and there's a new study out of the uk, south africa and japan, that finds it might be less likely to cause severe lung disease. we should note it hasn't been peer reviewed yet. how optimistic should we be about this? >> i think it's fascinating information, john. basically what the researchers are finding is that the omicron variant may be less likely to enter the lung cell.