Safety questions raised after volunteers developed unexplained neurological symptoms including limb weakness or ‘changed sensation’
Trials have resumed in some countries, though study remains on hold in US pending investigation
Symptoms that prompted the University of Oxford and partner AstraZeneca to pause trials evaluating their experimental coronavirus vaccine probably were not related to the shot itself, according to documents sent to participants.
Safety reviews were carried out when volunteers in the Oxford study developed unexplained neurological symptoms including limb weakness or “changed sensation”, a participant information sheet posted online by Oxford shows.
“After independent review, these illnesses were either considered unlikely to be associated with the vaccine or there was insufficient evidence to say for certain that the illnesses were or were not related to the vaccine,” the letter reads.
“In each of these cases, after considering the information, the independent reviewers recommended that vaccinations should continue.”
The details shed more light on an episode reported last week in the British trial and the safety data that triggered the halt.
AstraZeneca and Oxford have continued to face questions about the event, and their vaccine study remains on hold in the US pending a regulatory review, federal officials said. It is the first indication from Oxford as to the nature of the illness, which sparked widespread concerns about vaccine safety.
The interruption highlights the uncertainties researchers face on the road to developing vaccines aimed at restoring some normality to economies and societies smothered by the pandemic. Although temporary halts in such trials are not uncommon, the pause in the Oxford study heightens worries about when the first shots providing protection against the virus could be ready.
AstraZeneca Chief Executive Officer Pascal Soriot had said earlier that it was not clear whether the participant had a condition called transverse myelitis, after news reports cited it as a suspected diagnosis. US National Institutes of Health Director Francis Collins told a Senate committee last week that the trial had been halted due to a spinal cord problem.
The case is the second time a person taking part in the AstraZeneca study developed neurological symptoms, leading to a pause in research. The company said the independent panel monitoring the trial concluded the diagnosis was unrelated to the vaccine.
AstraZeneca declined to comment. Oxford representatives could not immediately be reached for comment.
Oxford and AstraZeneca are among the front-runners in the quest to develop a vaccine against the coronavirus. Like others, the partners are trying to accomplish in months what traditionally takes years.
AstraZeneca is also one of several companies taking part in the US government’s Operation Warp Speed programme to fast-track a shot. Data from final-stage trials are expected as soon as next month, and AstraZeneca’s Soriot said last week that the injection could still be available by the end of the year.
Governments wanting to revive limping economies are watching closely as vaccine testing goes forward, and US President Donald Trump has strongly suggested a shot will be available before the November 3 election.
US health officials offered conflicting estimates Wednesday of when Americans should expect vaccines to be broadly available, with one saying that the US public could be supplied by the April.
Trials of the Oxford-Astra vaccine resumed in the Britain over the weekend, while researchers in South Africa also restarted tests, saying that an independent safety committee concluded that the event was unlikely to be related to the vaccination.
The Serum Institute of India has received Indian regulatory approval to resume local trials and intends to restart in the next day or two, according to a person familiar with the matter who asked not to be named because the regulator’s decision is not public.
Close monitoring of the affected individuals and other participants will continue, according to the document.