Pfizer’s chief executive said on Friday that the company would not apply for emergency authorisation of its coronavirus vaccine before the third week of November, ruling out President Trump’s assertion that a vaccine would be ready before Election Day on November 3.

In a statement posted to the company website, the chief executive, Dr Albert Bourla, said that although Pfizer could have preliminary numbers by the end of October about whether the vaccine works, it would still need to collect safety and manufacturing data that would stretch the timeline.

Close watchers of the vaccine race had already known that Pfizer wouldn’t be able to meet the Food and Drug Administration’s requirements by the end of this month. But Friday’s announcement represents a shift in tone for the company and its leader.

Dr Eric Topol, a clinical trial expert at Scripps Research in San Diego, said while Pfizer officials had assured him that a vaccine would not be authorised before the polls, the company’s letter was “even more solid about their not being part of any political machinations”.