BANGALORE/NEW YORK (REUTERS) - Pfizer Inc said on Friday (Oct 16) it might file for US authorisation of the Covid-19 vaccine it is developing with German partner BioNTech in late November, making it unlikely a vaccine will be available before the US election as President Donald Trump has promised.

Pfizer said that it could say if the vaccine is effective as soon as this month based on its 40,000-person clinical trial but that it also needs safety data that will not be available until November at the earliest.

The Pfizer news, published in a letter from its chief executive on its website, lifted the US stock market and the company's shares. Shares were up slightly in rival vaccine maker Moderna Inc, which is close to Pfizer in its vaccine development.

"So let me be clear, assuming positive data, Pfizer will apply for Emergency Authorization Use (EUA) in the US soon after the safety milestone is achieved in the third week of November," Pfizer Chief Executive Albert Bourla said.

Trump has said repeatedly that there would be a vaccine available before the election, but health officials and companies had only said that data might be available this month.

The possibility of further delays was raised after trials for two rival vaccines were put on hold in the United States this fall.

The president's rush to a vaccine has also raised concerns that the US Food and Drug Administration, acting in haste, might not conduct an adequate review of the vaccine.

US health officials have sought to assuage those concerns out of fear that not enough Americans would take a vaccine early on. Earlier this month, the FDA formalised a requirement that the vaccine makers collect two months of safety data on one-half of trial participants.

Pfizer's comments on its time line raise the possibility of US authorisation of a coronavirus vaccine this year, a key step in controlling the Covid-19 pandemic, which has killed more than a million people and ravaged the global economy.

Moderna could also apply for an EUA this year. It has said that it may have interim data on its 30,000 person trial as soon as November.

Both companies are also applying for approval in Europe, where they are racing against AstraZeneca PLC.

AstraZeneca's US trial has been on hold since September.

After the FDA announced the two-month requirement on Oct 6, which was approved by the White House but undercut the likelihood of a vaccine before voters go to polls on Nov 3., Trump called the move a 'political hit job'.

In addition to safety and efficacy, the FDA will also examine Pfizer's manufacturing operations for the vaccine.

Bourla said the filing depended on several other factors, including initial data on effectiveness that might or might not be available by late October.

He said the company plans to share efficacy data with the public as soon as practical.

A BioNTech spokesman confirmed the time frame for the possible EUA application to the FDA.

Pfizer's shares rose 2.1 per cent in premarket trading, while BioNTech's US-listed shares were up 4 per cent before the opening bell.

Moderna was unchanged and US futures were higher.