“What I really think will be the final verdict will be the real-world data,” he  said. “We are expecting to see those toward the end of the year.”

On Wednesday, Pfizer and partner BioNTech SE released results of laboratory experiments on the highly transmissible variant’s evasion of vaccines that were obtained with a construct called a pseudovirus, Bourla said. The company is still working with the real virus while collecting evidence on how the vaccine performs in community use, he said.

The CEO expects that a third booster dose will “do the job” in restoring high levels of protection. That will likely accelerate booster-shot drives around the world and may buy time for drugmakers to develop strain-specific vaccines.

The real-world efficacy data will help determine whether a new vaccine that specifically targets omicron is needed, Bourla said. The companies would be able to produce very large quantities of such a shot by March, he said.

Read More: Third Dose of Pfizer-BioNTech Shot Key to Fight Elusive Omicron

Meanwhile, Pfizer is also making headway on bringing its experimental Covid-19 antiviral treatment to market. The company expects to provide final clinical trial results to U.S. regulators “within several days,” Bourla said. Pfizer has already shared interim results with the Food and Drug Administration that show the pill, Paxlovid, reduced risk of hospitalization or death by 89% among high-risk people who contracted Covid.

Merck & Co.’s competing drug candidate showed a significant drop in efficacy between its interim and final analyses, and the FDA has asked Pfizer for more data on its pill. Still, Bourla said he’s optimistic that regulators could make a decision on Paxlovid before the end of the year.

–With assistance from David Westin and Robert Langreth.