An “October surprise” in American politics is the term for an unexpected event that occurs just before the November poll, shifting the vote's outcome.

Many remain highly sceptical that a safe vaccine could be delivered so soon, even though the President has spent months pushing health authorities to fast track the process under his aptly titled program, Operation Warp Speed.

However, the Biden campaign accepts an announcement is possible before the election, and is preparing to frame the debate around the likelihood of this happening.

“My guess is he is going to announce a vaccine, he’s going to say it’s going to be available around election day, he’s going to hype it,” Biden said at his latest public appearance last week.

Asked about the matter today, Biden campaign senior spokeswoman Symone Sanders also didn’t reject the idea of a vaccine being available soon, opting instead to focus on the need to ensure Americans had equitable access to it.

“We all want a vaccine, but we want that vaccine to be safe and when the vaccine is eventually available we want it to be equitably distributed,” she told Fox News.

The debate comes as coronavirus continues to spread across the US, which has now recorded more than 6.25 million infections and almost 190,000 deaths.

As crowds gathered this weekend for the Labour Day long weekend, health authorities feared that outbreaks will emerge within weeks, while universities across the US have already seen a significant uptick in cases.

With eight weeks left in the campaign, Trump aides are hoping a vaccine could help bolster their messaging on the economy, which received a modest boost last week when the US unemployment rate fell under 10 per cent for the first time since March.

Under Operation Warp Speed, the administration’s goal was to deliver 300 million doses of “safe and effective vaccines,” with the initial doses available by January 2021.

Corporate pharmaceutical giants have been given billions of dollars to support the development, manufacturing, and trials of a potential vaccine.

Amid concern about the process being rushed, some of those companies – including Johnson and Johnson, Pfizer Inc and Moderna – are planning to issue a public pledge not to seek government approval until their shots are found to be safe and effective.

Biden’s running mate, Senator Kamala Harris, was not convinced the pledges could stop the politicisation of any vaccine.

Harris told CNN in an interview today: “I would not trust Donald Trump and it would have to be a credible source of information that talks about the efficacy and the reliability of whatever he’s talking about.”

Former CDC director Dr Tom Frieden said it was sensible for the administration to begin telling states to prepare for the vaccine as the process was “complicated”.

He added: “It's in the company's interest; it's in the public's interest; it's in a politician's interest that we can trust the institutions that we've trusted for decades to base decisions on science.

“That’s the most effective way for us to fight this virus and we can do that by joining together... There's only one enemy here – and that's the virus.”