Drug giant AstraZeneca said Tuesday it had paused a trial of its coronavirus vaccine because of an unexplained illness in one of the volunteers.
It’s a standard precaution in vaccine trials, meant to ensure experimental vaccines don’t cause serious reactions among volunteers.
“As part of the ongoing randomized, controlled global trials of the Oxford coronavirus vaccine, our standard review process triggered a pause to vaccination to allow review of safety data,” the company said in a statement sent to CNN.
“This is a routine action which has to happen whenever there is a potentially unexplained illness in one of the trials, while it is investigated, ensuring we maintain the integrity of the trials,” the statement added.
“In large trials, illnesses will happen by chance but must be independently reviewed to check this carefully. We are working to expedite the review of the single event to minimize any potential impact on the trial timeline. We are committed to the safety of our participants and the highest standards of conduct in our trials.”
Earlier Tuesday, AstraZeneca joined eight other companies in signing a pledge promising they would not seek premature government approval for any coronavirus vaccine. They promised they would wait until they had adequate data showing any potential vaccine worked safely to prevent infection.
The AstraZeneca vaccine is one of three coronavirus vaccines in late-stage, Phase 3 trials in the US.
It was not immediately clear if the pause involved only US trial sites or all of the company’s trial sites around the world. A Data and Safety Monitoring Board usually monitors trials for adverse events and can order a pause or halt to a trial, but AstraZeneca did not say who had stopped the trial.
An AstraZeneca spokesperson later said the illness affected a participant in Britain, but said all of the company’s trials of the vaccine globally would be paused.