"We definitely saw variants coming. I think what one referred to, what was not anticipated was the extent of the mutations and the amino acid [ACE-*] substitutions in omicron, which is really unprecedented," Fauci said. "It kind of came out of nowhere, where you have a virus that has 50 mutations, 30 of which are in the spike protein and 10 or 12 of which are in the receptor binding domain. I mean, to me, that's really quite unprecedented."