General Gustave Perna is chief operating officer of Operation Warp Speed.
On Saturday, he apologized for a "planning error" that caused dozens of states to expect more vaccine doses than they'll actually get.
Dozens of states have said they will receive 30% to 40% fewer doses of Pfizer's vaccine next week than they were expecting.
Perna said that was a result of estimates he gave for planning purposes that wound up being incorrect.
"I failed," Perna said.
