Researchers at the University of Oxford believe they have made a breakthrough after discovering the jab could provide "double protection" against the virus, the Daily Telegraph reported.
Health secretary Matt Hancock said teams were working towards a "best case scenario" of a vaccine being made available sometime this year, although conceded it was more likely in 2021.
Speaking on ITV's Peston on Wednesday evening, Hancock said: "We're all working towards the best case scenario, we're all giving AstraZeneca and the team at Oxford, and the Imperial vaccine, every possible support, we're working with the other potential vaccines around the world, in America, and Germany, and the Netherlands.
"We're working with them to ensure that if they come off first, that we'll get access to them here.
"But this is an inexact science and it's at risk.”
He said the most clinically vulnerable, such as the elderly, and healthcare workers would be the first to get the vaccine, and added that he is expanding the list of professionals who can legally vaccinate, which will include not just GPs but also technicians, nurses and pharmacists.
Nurses and pharmacists can already administer certain vaccinations without a prescription from a doctor.
According to the Daily Telegraph, the phase one trial in healthy adult volunteers, which began in April, showed the vaccine generated an immune response, with blood samples indicating it stimulated the body to produce both antibodies and "killer T-cells”.
The combination of the two responses "will hopefully keep people safe", a source told the paper.
David Carpenter, chairman of the Berkshire Research Ethics Committee, which approved the Oxford trial and continues to work with scientists on amendments, told the paper that the team were "absolutely on track”.
He added: "Nobody can put final dates… things might go wrong but the reality is that by working with a big pharma company, that vaccine could be fairly widely available around September and that is the sort of target they are working on.”