AstraZeneca has paused all clinical trials of the Covid-19 vaccine it is developing with Oxford university after a participant in the UK section of the study suffered a suspected serious adverse reaction.
The UK-based drugmaker voluntarily put the trial on hold after the discovery of the sick participant, who fell ill with a rare inflammatory condition called transverse myelitis, according to two people familiar with the trial.
AstraZeneca said it was reviewing the event to ensure it would not result in a significant delay. People associated with the trial said it could resume early next week, after the study’s independent data monitoring board has investigated.
Chief executive Pascal Soriot on Wednesday described the suspension of the trials as a “temporary pause” and said the case was being investigated.
AstraZeneca had been on track to become one of the first to deliver results from a large vaccine trial. The White House has considered fast-tracking the process for its vaccine, ahead of the US presidential election, according to people familiar with the matter.
Shares in AstraZeneca fell in intraday trading in London on Wednesday but ended the day 0.5 per cent higher. Its New-York listed shares had fallen sharply in after-hours trading on Tuesday after trade publication STAT first reported the trial had been stopped.
The drugmaker described the pause as “routine action which has to happen whenever there is a potentially unexplained illness in one of the trials”. It added that “in large trials, illnesses will happen by chance but must be independently reviewed to check this carefully”.
It is not unusual for vaccine trials to be paused. This is the second time it has happened to the Oxford-AstraZeneca trial. “We expect more pauses before it finishes,” said one person close to the process.
Jeremy Farrar, director of the Wellcome Trust, said: “It is very unusual to go through a vaccine trial and not to pause it.”
But in the most scrutinised vaccine development process ever, the sign of potentially negative side-effects is drawing wide attention.
“The trial was expected to read out by November (as an upper estimate) and potentially in the next few weeks,” analysts at Shore Capital wrote. “However, any suspension to the trial is likely to lead to delays in these timelines.”
Even if AstraZeneca’s vaccine is eventually approved, concerns about side-effects may deter people from having it.
Experts have raised concerns that approval of a vaccine could be rushed if the process becomes politicised, although the pharmaceutical companies and the US Food and Drug Administration have insisted approval would only be given based on solid scientific evidence.
Joe Biden, the Democratic presidential candidate, and Kamala Harris, his vice-presidential running mate, on Tuesday called on the Trump administration to ensure that “politics will play no role in the approval and distribution of a safe and effective Covid-19 vaccine”.
AstraZeneca is commercialising a vaccine created by researchers at Oxford university under a deal signed in April. To speed up the process, the drugmaker has begun manufacturing it before the trials are complete or the vaccine is approved.
The partnership — which has received more than $1bn in funding from the US Biomedical Advanced Research and Development Authority — has agreed to deliver more than 300m doses to the US government.
The UK has ordered 30m doses. Matt Hancock, the UK health secretary, this week said it would “most likely” be available in early 2021.
Data from the vaccine’s earliest trial looked promising, producing a robust immune response and only mild side-effects.
The earlier trials did not include sites within the US but late last month the next stage of the trial, which will have 30,000 participants, began enrolling in the US.
Paul Offit, an infectious disease expert on the FDA’s vaccine advisory committee, said AstraZeneca would need to examine whether the side-effect was purely a reaction to the vaccine or was also related to the participant’s medical history.
Transverse myelitis, an inflammation of the spinal cord, has been associated with other vaccines. A study showed that 37 cases were reported over 40 years after different vaccinations including against hepatitis B, measles-mumps-rubella and diphtheria-tetanus-pertussis.