Pfizer CEO Albert Bourla was confident in June about the ability of his company’s vaccine to protect against the highly contagious delta variant, as it marched across the globe and filled U.S. hospitals with patients.
“I feel quite comfortable that we cover it,” Bourla said.
Just weeks later, Pfizer said it would seek authorization for a booster shot, after early trial results showed a third dose potentially increased protection. At the end of July, Pfizer and BioNTech announced findings that four to six months after a second dose, their vaccine’s efficacy dropped to about 84%.
Bourla was quick to promote a third dose after the discouraging news, saying he was “very, very confident” that a booster would increase immunity levels in the vaccinated.
There’s one hitch: Pfizer has not yet delivered conclusive proof to back up that confidence. The company lacks late-stage clinical trial results to confirm a booster will work against covid variants including delta, which now accounts for 93% of new infections across the U.S.