this since the beginning, since january, february, that when you gave those first two doses so close together, you guaranteed that immunity would wane and would require a third immunization in order to give you that 30-fold rise in virus neutralizing antibodies and provide immune responses. that's not what's happening. it should have been messaged from the beginning it was a three-dose vaccine. i'm not convinced we'll need bosters every year. it could be three and done. as dr. fauci points out, we won't know till we know. but i have some optimism that three doses may be adequate for this right now. >> interesting. good to see you, dr. hotez. thanks. >> thank you. coming up for us, russia warning of a return to military confrontation over ukraine as the united states tells moscow that there will be serious consequences if they move the invade ukraine again. the very latest from the region