Final clinical trials for a coronavirus vaccine, developed by AstraZeneca and Oxford University, have been put on hold after a participant had an adverse reaction in the UK, the BBC reports.
AstraZeneca described it as a “routine” pause in the case of “an unexplained illness”.
The outcome of vaccine trials is being closely watched around the world.
The AstraZeneca-Oxford University vaccine is seen as a strong contender among dozens being developed globally.
Hopes have been high that the vaccine might be one of the first to come on the market, following successful phase 1 and 2 testing.
This is the second time the Oxford coronavirus vaccine trial has been put on hold. Such events are routine in major trials, and happen any time a volunteer is admitted to hospital when the cause of their illness is not immediately apparent.
It is thought the trials could resume in a matter of days.