Albert Bourla, chief executive of Pfizer, said in an open letter that he wanted to “further clarify the development timelines” of the vaccine, which is being tested in some 38,000 people worldwide.
No manufacturer outside of Russia and China has achieved regulatory approval for a vaccine globally, making Pfizer a leader in the race.
While Mr. Bourla’s statement showed that the company’s trial was well advanced, it also clarified that the shooting would not be available until after the US presidential election on November 3.
President Donald Trump has previously said a vaccine will be available “within a few weeks”, while officials have discussed a pre-election vaccination campaign. Pharmaceutical executives pushed back on what they described as the politicization of the vaccine development process and alleged White House pressure to speed up clinical trials.
This month, in a note to staff seen by the Financial Times, Bourla said the “amplified political rhetoric” around vaccine development and timing “is undermining public confidence.”
In the letter released Friday, Bourla said Pfizer could find out if the vaccine was working at the end of October, but warned that the data “could come sooner or later depending on how infection rate ”among trial participants.
“To ensure public confidence and clear up great confusion, I believe it is essential that the public understand our estimated timelines,” he added.
Mr. Bourla pledged to publish a full analysis of the results, whether positive or negative, “as soon as possible”.
To receive emergency clearance from the U.S. Food and Drug Administration, Pfizer will need to submit safety data on at least half of the trial participants, showing how they responded for two months after the final dose.
The vaccine from Pfizer and BioNTech, which is based on new mRNA technology, is given as two separate injections.
The companies said they would be able to produce 100 million doses worldwide this year, and at least 1.3 billion next year. The United States has signed a deal with Pfizer to secure 600 million doses, while the EU is negotiating a deal for 200 million doses. The UK and Japan are among several other countries that have also signed agreements with companies.
This month, the FDA’s European counterpart, the EMA, accelerated its vaccine approval process.