The Phase III clinical trials for a coronavirus vaccine, developed by AstraZeneca and Oxford University, have been paused after a participant had an adverse reaction in the UK.

As part of the ongoing randomized, controlled clinical trials of the AstraZeneca Oxford coronavirus vaccine, AZD1222, a standard review process has been triggered, leading to the pause of vaccination across all trials to allow an independent committee to review the safety data of a single event of an unexplained illness that occurred in the UK Phase III trial. First to report about this was the health site Stat News, writing that details of the UK participant’s adverse reaction were not immediately known, but quoted a source as saying they were expected to recover.

“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. In large trials illnesses will happen by chance but must be independently reviewed to check this carefully,” stated AstraZeneca to Stat News.

“At AstraZeneca we put science, safety and the interests of society at the heart of our work. This temporary pause is living proof that we follow those principles while a single event at one of our trial sites is assessed by a committee of independent experts. We will be guided by this committee as to when the trials could restart, so that we can continue our work at the earliest opportunity to provide this vaccine broadly, equitably and at no profit during this pandemic,” says Pascal Soriot, Chief Executive Officer, AstraZeneca.

Recently expanded Phase 3 trial

AstraZeneca’s move to Phase 3 testing in recent weeks has involved some 30,000 participants in the US as well as in the UK, Brazil and South Africa.

Read more: AstraZeneca expands its US COVID-19 vaccine trial

All international trial sites have now been put on pause while an independent investigation reviews the safety data before regulators decide whether the trial can restart, the BBC’s Medical Editor Fergus Walsh reports.

Read more: Pharma CEOs sign historic COVID-19 pledge

Photo of Pascal Soriot: AstraZeneca