A subsequent booster jab kick-started an antibody response within 28 days, enabling the virus to be attacked when circulating in the blood or lymphatic system.
The Oxford vaccine unlike the Pfizer/BioNTech drug does not have to be stored at around -70C prior up to a few days before being administered.
Prof Andrew Pollard, study lead from the University of Oxford, told the BBC he was “absolutely delighted with the results” showing a strong immune response “even in those over 70 years of age”.
On whether the vaccine protects people against Covid-19, he said they were “not there yet” but the data would probably be released “before Christmas”.
Prof Pollard said there was “no competition” with other vaccines, adding that multiple vaccines needed to be successful.
“We will need all of them to protect people around the globe,” he said.