Ten thousand volunteers are needed to take part in a new stage of a Covid-19 vaccine trial.
A new phase-three trial for a vaccine created by US biotech company Novavax was started on Thursday, marking the second phase-three trial to take place in the UK.
As part of the research, 10,000 people will be invited to take part in the new phase.
Phase-three trials require a large number of people to test the safety and effectiveness of the potential vaccine across a community.
They will be held across the country including in Greater Manchester, London, Glasgow and Belfast.
Sixty million doses of the vaccine have been secured by the Government, to be manufactured in Stockton-on-Tees, Co Durham, if it is successful.
The volunteers had previously signed up to the NHS Covid-19 vaccine research registry, created in July to allow people to express their interest in taking part in a clinical trial and to be contacted by researchers.
More than 250,000 people have since signed up, but researchers are encouraging more people to volunteer, particularly people from black, Asian and minority ethnic backgrounds, those with underlying health conditions and people over 65.
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Business Secretary Alok Sharma said: "I am incredibly proud of the 250,000 volunteers who have signed up to play their part in the global fight against coronavirus.
"Our scientists and researchers are working day and night to find a vaccine that meets the UK's rigorous safety standards, but we need even more people from all backgrounds and ages to sign up for studies to speed up this life-saving research.
"The more people that sign up, the quicker we can find a safe and effective vaccine, defeat this virus and protect millions of lives."
