US pharmaceutical giant Pfizer expects to file for emergency use authorization for its Covid-19 vaccine in late November, around two weeks after the November 3 US presidential election, it said Friday.

The company said it hopes to move ahead with the vaccine after safety data is available in the third week of November, immediately lifting the company's shares two percent in the US.

"So let me be clear, assuming positive data, Pfizer will apply for Emergency Authorization Use in the US soon after the safety milestone is achieved in the third week of November," the company's chairman and CEO Albert Bourla said in an open letter.

The announcement means the United States could have two vaccines ready by the end of the year, with Massachussetts biotech firm Moderna aiming for November 25 to seek authorization. 

The Food and Drug Administration (FDA), which authorizes pharmaceuticals for distribution in the US -- asked vaccine developers last week to spend two months monitoring for serious side effects after the second dose is given to trial participants.

The FDA will require the vaccine to prove effective and safe, while Pfizer will have to demonstrate it is capable of producing large scale production. 

Pfizer and Modern, both funded by the US government, launched Phase 3 of their clinical trials at the end of July, and both have started production of doses.

They aim to be in a position to deliver tens of millions of doses to the US by the end of the year.

Bourla said the Pfizer trial, involving 30,000 participants, might produce results on the vaccine's efficacy within the next two weeks. 

"I've said before, we are operating at the speed of science. This means we may know whether or not our vaccine is effective by the end of October," Bourla said.

Pfizer, which is partnering with German company BioNTech on the research, gained more than two percent in online trading ahead of the opening of US markets.