UK’s pharma giant AstraZeneca on Tuesday said that it had voluntarily paused a randomised clinical trial of its COVID-19 vaccine in what it called a routine action after a volunteer developed an ‘unexplained illness’.

The company has paused a late-stage trial, health news website Stat News reported. The ‘standard review process triggered a pause to vaccination to allow the review of safety data,’ quoted an AstraZeneca spokesperson as saying. It added that in such big trials, illnesses will sometimes happen by chance but must be reviewed self-reliantly.

The spokesperson said, "We are working to expedite the review of the single event to minimise any potential impact on the trial timeline.” It was not clear where the patient was or the intensity of their illness.

Holds during clinical trials are not uncommon but this is thought to be the first time it has happened for a vaccine trial of the novel coronavirus.

AstraZeneca is one of nine companies in the world currently in late-stage Phase 3 trials for their COVID-19 vaccine trials.