Children and older adults are to be included in the second phase of vaccine trials to protect against coronavirus.
The first phase of the University of Oxford trial began in April, with 1,000 people given the jab.
Now, more than 10,200 adults, including over 70s and five- to 12-year-olds – will be enrolled in the study, to see the effects on their immune system.
Trials of the same vaccine on monkeys appear to have given them protection against the disease.
The scientists behind it have previously said they are aiming to have at least a million doses of a coronavirus vaccine by September this year.
But the UK government has repeatedly said there are no guarantees – and a vaccine could still be some way off.
And most experts still estimate it will take 12 to 18 months to develop and manufacture a vaccine.
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Adults in the trial will receive one or two doses of either the new vaccine – ChAdOx1 nCoV-19 – or another licensed vaccine.
Researchers will then compare the number of infections in both groups.
And this could take between two and to six months, depending on how many people are exposed to the virus.
The age range of participants has been expanded to include those aged:
Sarah Gilbert, professor of vaccinology, at the Jenner Institute, said: “We have had a lot of interest already from people over the age of 55 years who were not eligible to take part in the phase-one study.
“And we will now be able to include older age groups to continue the vaccine assessment.
“We will also be including more study sites, in different parts of the country.”