“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 company said.

AstraZeneca offices in Cambridge, England. | Alastair Grant/AP Photo

AstraZeneca has paused clinical trials of its coronavirus vaccine to review safety data while it investigates a "single event" of illness among a person enrolled in one of its studies.

"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 company said in a statement Tuesday. "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 minimise any potential impact on the trial timeline."