The UK arm of the study is aiming to recruit 6,000 participants among a total of 30,000 people globally, scientists leading the UK trial said. Volunteers will be recruited at 17 sites across the UK.
They will be given the first dose of either a placebo or the experimental shot, currently called Ad26COV2, followed by a second dose or placebo 57 days later, said Saul Faust, a professor of pediatric immunology and infectious diseases who is co-leading the trial at the University Hospital Southampton.
If the results of the single-shot trial are positive, the company said it could simplify the distribution of millions of doses compared with leading rivals requiring two doses. The efficacy of a double-dose vaccine could be affected if people fail to return to get their second shot.