Pfizer CEO Albert Bourla said Friday there wasn't clear evidence yet on whether it would be safe to forgo a second dose of its coronavirus vaccine or delay administering it, a day after a study showed robust immunity after just one shot.
"We don't know what would happen if we didn't administer the second dose," Bourla said, reports the Forbes.
"We don't think it will work. But we're looking at it."
On Thursday, a study in Israel showed that a single shot of the Pfizer-BioNTech vaccine was 85% effective against symptomatic Covid-19 within 15 to 28 days after it was administered.
Pfizer and BioNTech did not respond to requests for further comment.
Pfizer and BioNTech currently recommend two doses of the vaccine, administered 21 days apart, for the 95% efficacy rate that was shown in clinical trials.
But the study — conducted by the Israeli government-owned Sheba Medical Center and published in the medical journal The Lancet — could fuel debates over whether governments should delay a second dose in order to make a limited supply of vaccines available to more people.
Researchers in the study of more than 9,000 healthcare workers found a 75% reduction in symptomatic and asymptomatic cases after one dose.