Late-stage trials for a leading coronavirus vaccine have been suspended after a study participant suffered a “potentially unexplained illness”.
AstraZeneca has put on hold phase three trials of a vaccine being developed in collaboration with the University of Oxford.
The Australian Government last month signed an agreement with the UK-based company to secure the potential COVID-19 vaccine if its trials prove successful.
In a statement, AstraZeneca said it “voluntarily paused” the phase 3 clinical trial which kicked off in July to allow a review of the “single event” 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,” the statement said. “In large trials illnesses will happen by chance but must be independently reviewed to check this carefully.”
The Australian Government had secured 33.8 million doses of the Oxford vaccine for local manufacturing. It also locked in 51 million doses of a potential vaccine being developed by the University of Queensland and CSL.
The potential total 84 million doses would be rolled out, free of charge, in stages across next year, pending successful trials, with the Government flagging that 3.8 million doses of the Oxford vaccine could be rolled out as early as January.
However, vaccine experts on Monday cautioned that the Federal Government’s timeframe was “ambitious” and “optimistic”, with most phase 3 trials taking at least a year to complete.
The Oxford vaccine produced an immune response in its first human trials, underlining its position as one of the leading candidates in the race to combat a virus that has led to hundreds of thousands of deaths and crippled the global economy.
Late last month, AstraZeneca began recruiting 30,000 people in the United States for its largest study of the vaccine. It also is testing the vaccine in thousands of people in Britain, and in smaller studies in Brazil and South Africa.
The trial’s lead scientist, Andrew Pollard, previously said trial data for the possible vaccine could potentially be given to regulators this year. It is unclear whether today’s announcement will affect the timeline, if at all.
Australian company CSL said it planned to start manufacturing the Oxford vaccine candidate as early as next month in preparation for its rollout in Australia.
It is understood the company does not expect today’s announcement to impact that plan.
Australian vaccine expert Tony Cunningham, who has managed multiple phase 3 trials across the world, told the ABC these types of “severe adverse events” were common.
He said vaccine trials generally saw half receive the vaccine and half receive a placebo, and as yet it was unclear which group the unexplained illness came from.
“They’ll have a data monitoring safety board,” he said. “People who are arm’s length from the trials, and they will assess these events to determine what happened.
“But this shows that you need to do these things properly. You’re dealing with, potentially, the health of hundreds of millions of people, and that’s why these trials take time. They can’t be rushed”
Australia’s Deputy Chief Medical Officer Nick Coatsworth said the move “by no means puts that vaccine completely off the table”.
“It would be fairly standard process if there’s a very severe reaction and they are not sure whether it’s attributable to the vaccine or not, to gather the information and holding the trial for the moment,” he said on Seven’s Sunrise program.
“We’ve got to keep in mind the tens of thousands of people have now received this vaccine, so this is a testimony to the rigor and the safety focus that people are putting on vaccine development.”
He said the Government was investing in “multiple technologies, multiple potential vaccines” to offset setbacks encountered by any single vaccine.
There are more than 160 vaccine candidates in various stages of development around the world.
Two vaccines are in huge, final-stage tests in the United States — one made by Moderna Inc and the other by Pfizer and Germany’s BioNTech.
Those two vaccines work differently than AstraZeneca’s, and the studies already have recruited about two-thirds of the needed volunteers.
AstraZeneca’s US-traded shares fell more than 6 per cent in after-hours trading following reports of the trial being paused.