Phase 3 trials of a coronavirus vaccine developed by British drugmaker AstraZeneca and Oxford University were put on hold, the company announced Tuesday, due to a suspected serious adverse reaction in a participant.

AstraZeneca spokeswoman Michele Meixell said: “As part of the ongoing randomized, controlled global trials of the Oxford coronavirus vaccine, our standard review process was triggered and we voluntarily paused vaccination to allow the review of safety data by an independent committee.”

“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.”

“We are working to expedite the review of the single event to minimize any potential impact on the trial timeline,” she added.

AstraZeneca did not immediately give details as to the nature of the adverse reaction, although the participant is expected to recover.

The vaccine had previously been reported to be available perhaps as early as January 2021.

The incident highlights the risks in the push to quickly produce a vaccine for Covid-19, which has claimed the lives of nearly 890,000 people and disrupted economies and daily routines worldwide.

Due to the safety issues involved, vaccine trials typically take months and involve tens of thousands of test subjects. (TASS)