Doses of the vaccine, called AZD1222, were given to 1,077 healthy adults aged between 18 and 55 in five UK hospitals in April and May as part of the phase one clinical trial for the vaccine being developed by AstraZeneca and scientists at the University of Oxford.
The results – published in The Lancet journal on Monday – show they induced strong antibody and T-cell immune responses for up to 56 days after they were given.
T-cells are crucial for maintaining protection against the virus for years.
Scientists found the response could be even greater after a second dose of the vaccine.
The UK government has made a deal with AstraZeneca and the University of Oxford to secure access to 100 million doses of the vaccine.
Professor Andrew Pollard, who is leading the study at the University of Oxford, said: “The immune system has two ways of finding and attacking pathogens – antibody and T cell responses.
“This vaccine is intended to induce both, so it can attack the virus when it’s circulating in the body, as well as attacking infected cells.
“We hope this means the immune system will remember the virus so that our vaccine will protect people for an extended period.
“However, we need more research before we can confirm the vaccine effectively protects against SARS-CoV-2 infection, and for how long any protection lasts.”
Although these results are from phase one of the trials, phase two testing is already underway in the UK and phase three testing on volunteers in Brazil and South Africa is also taking place.
AstraZeneca’s vaccine is among the leading candidates among several others around the world, including an injection being developed by China’s Sinovac Biotech, another from state-owned Chinese firm Sinopharm and one from US biotech firm Moderna.
The UK government has also secured early access to 90m COVID-19 vaccine doses through partnerships with pharmaceutical companies, including 30m of one being developed by BioNTech and Pfizer, and 60m from Valneva which has a factory in Scotland.
Source: Sky News