AstraZeneca has put its trial of a Covid-19 vaccine on pause after a suspected serious adverse reaction in a study participant, health news website Stat News reports.

It quoted an AstraZeneca spokesperson as saying in a statement that the "standard review process triggered a pause to vaccination to allow review of safety data."

The highly anticipated vaccine candidate being developed by Oxford University is in the late-stage phase three trials.


Serious adverse events are suspected reactions to vaccines or drugs that require hospitalisation, are life-threateningly or deadly.

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It's unclear what the exact nature of the reaction was, but a person familiar with the matter told Stat News that the person is expected to recover.

Trial holds are not uncommon.

It is still a setback to hopes for a vaccine to be ready in the coming months. The AstraZeneca project was considered by the World Health Organisation to be the leading option worldwide.

Other key candidates are being developed by Pfizer, and Moderna.

The pause on AstraZeneca's trial could delay the project's results and completion.

The Daily Mail reports that market confidence in the pharma giant has taken a hit.

Shares for AstraZeneca plummeted by 8 per cent in after-hours trading.