Possible adverse reaction: Oxford University Covid-19 vaccine trial put on hold

LONDON: The development of a promising Covid-19 vaccine has been put on hold due to a possible adverse reaction in a trial participant.

A spokesman for AstraZeneca, the company working with a team from Oxford University, told the Guardian the trial has been stopped to review the "potentially unexplained illness" in one of the participants.

The spokesman stressed that the adverse reaction was only recorded in a single participant and said pausing trials was common during vaccine development. "As part of the ongoing randomised, controlled global trials of the Oxford coronavirus vaccine, our standard review process was triggered and we voluntarily paused vaccination to allow review of safety data by an independent committee," the spokesman said.

"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.

"We are working to expedite the review of the single event to minimise any potential impact on the trial timeline. We are committed to the safety of our participants and the highest standards of conduct in our trials."

The vaccine, which had been expected to be publicly available as early as January, is one of two projects on which the Australian government plans to spend $1.7bn as part of a deal to ensure free vaccines for all citizens.

On Monday, the Morrison government committed to buying 33.8m doses of the vaccine if it was proved to be effective. The BBC reported this is the second time this particular vaccine has been paused since trials began in April.

Details of the unexplained illness have not been released, however a New York Times report notes that one volunteer in the UK program has developed transverse myelitis - an inflammation across the spinal cord.

However AstraZeneca have not commented on this, and there is no evidence the patients with transverse myelitis is the patient that has triggered the study halt. On Wednesday, Australia's health minister sought to address any concerns about the pause, noting his government is "pursuing a diversified Covid-19 vaccine strategy, ensuring that Australia is well placed to access a successful vaccine". Responding to the announcement, Australia's deputy chief medical officer Nick Coatsworth said the trial's pause "by no means puts that vaccine completely off the table".