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, involving 1,000 healthy adults aged 55 and under.
Now more than 10,200 people – 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 some protection against the disease.
The animals had less of the virus in their lungs and airways, but it is not certain this finding will translate to people.
The scientists behind the vaccine 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.
There are more than 100 experimental vaccines against Covid-10 currently being developed worldwide.
See also first human clinical trials of Covid-19 vaccine about to start