AstraZeneca-Oxford Covid-19 vaccine study paused after patient illness

9 Sep 2020

Image: © Roland Magnusson/

Development of the Covid-19 vaccine candidate from AstraZeneca and Oxford University has halted after a trial participant had an adverse reaction.

One of the most high-profile Covid-19 vaccine trials has been put on hold out of “an abundance of caution”. According to Stat News, one of the participants in the AstraZeneca and University of Oxford Covid-19 vaccine trial experienced an adverse reaction. While it is not yet known what the reaction was, sources told the health news website that the person is expected to recover.

In a statement, AstraZeneca said the decision to pause the phase-three trial was “a routine action” that is common in vaccine trials when there is an unexplained illness.

“In large trials, illnesses will happen by chance, but must be independently reviewed to check this carefully,” the company said. “We are working to expedite the review of the single event to minimise any potential impact on the trial timeline.”

A source speaking with Stat News said the finding is having an impact on other AstraZeneca trials that are underway, in addition to trials underway with other vaccine manufacturers. A further statement from the pharma company went on to stress that it had voluntarily paused the trial.

Currently, there are nine phase-three trials underway for Covid-19 vaccine candidates. A phase-three trial involves giving the vaccine candidate to thousands of people to determine how effective it may be or if there are any side effects.

Further research needed

Last week, AstraZeneca announced that it had initiated phase-three trials in the US, with plans to recruit up to 30,000 people to help test the safety and efficacy of the vaccine candidate. It is also conducting trials in the UK, Brazil and South Africa.

The AZD1222 vaccine uses an adenovirus that contains a gene of a SARS-CoV-2 protein and is designed to induce the immune system to respond to the virus.

Findings on phase-one and phase-two trials published last July in The Lancet said that approximately 60pc of 1,000 study participants given the AZD1222 vaccine experienced some side effects.

This included headaches, fever, muscle pain and injection reactions, which are deemed either mild or moderate and were reported to have subsided during the study. A serious adverse reaction is typically defined as one that requires hospitalisation or a life-threatening illness.

The AstraZeneca news comes a few days after Pharmaceutical giants GSK and Sanofi announced they had begun phase-one and two clinical trials for their adjuvanted Covid-19 vaccine. The vaccine candidate being developed by the two companies uses the same recombinant protein-based technology as one of Sanofi’s existing seasonal flu vaccines, along with GSK’s adjuvant technology.

Colm Gorey was a senior journalist with Silicon Republic