April 16 (UPI) -- People who have received the Pfizer-BioNTech COVID-19 vaccine will likely need a third dose of the shot, possibly within a year, Pfizer CEO Albert Bourla said.They may also need annual booster shots for maximum protection against infection, Bourla told CNBC on Thursday.
The Pfizer-BioNTech vaccine was the first one cleared for use in the United States.
"A likely scenario is that there will be likely a need for a third dose, somewhere between six and 12 months and then from there, there will be an annual revaccination," Bourla said.
However, "all of that needs to be confirmed and, again, the variants will play a key role," he said.
The Pfizer-BioNTech vaccine, which was granted an emergency use authorization by the U.S. Food and Drug Administration in December, was found to offer up to 95% protection against severe infection for up to six months in clinical trials.
New virus variants could weaken that immunity, even though the shot has proven effective against the most common new COVID-19 strain, the so-called "U.K. variant," in recent studies.
That could change as new variants emerge because the coronavirus, like all viruses, will continue to mutate, experts have said.
Bourla's comments echo those made by David Kessler, who heads the U.S. COVID-19 response team, during testimony before Congress on Thursday.
People in the United States who received the Pfizer-BioNTech shot should expect the need for a booster dose at some point, he said.