It's hoped a Covid-19 vaccine could be available by early 2021, with British health care staff and at-risk patients potentially being immunised within the next few weeks.
The third stage of clinical trials for the vaccine, developed by drugmaker AstraZeneca and Oxford University's Jenner Institute, is already at an advanced stage, according to The Guardian.
The third trial will compare participants who receive the shot compared to those who received a placebo.
The trials involve nine different sites and 10,000 volunteers across the UK, as well as Brazil and South Africa. Further trials are also being carried out in India and the US.
The AstraZeneca trial in the US was temporarily halted after two participants fell ill during the trial. It was later established that their illnesses were not linked to the trial.
Adrian Hill, the founder and director of the University of Oxford's Jenner Institute, said two successful clinical trials have already established its safety and its ability to trigger a strong immune response.
Leading US infectious diseases expert Dr Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, said today that they "will know whether a vaccine is safe and effective by the end of November, the beginning of December".
However, he warned that the amount of doses - should it be available in the suggested timeframe - will "not certainly be enough to vaccinate everybody".
"You’ll have to wait several months into 2021," Fauci said.
It comes after the Mail on Sunday publised a memo by Glen Burley, the chief executive of a group of Midlands hospitals, earlier this month calling for National Health Service staff to prepare for the rollout of a Covid-19 vaccine programme in early December.
“The latest intelligence states a coronavirus vaccine should be available this year with NHS staff prioritised prior to Christmas,” according to Burley's memo.
However, UK National Health Service sources called the potential rollout of the vaccine premature.
“There is no progress at all, no date, no national steer and only frustration,” a senior official at one of the major NHS trusts said.
Hill said researchers are planning to seek emergency authorisation to distribute the vaccine to vulnerable patients based on interim results, with the rest of the population to be vaccinated as early as next year.
"We're going to vaccinate high-risk individuals before we vaccinate the young, the fit and healthy who are at lower risk. I think most countries will do that," he said.