A World Health Organization official on Tuesday said that the decision by AstraZeneca to pause global trials of its experimental coronavirus vaccine after an unexplained illness showed the firm was prioritising safety.
“This is what we want to see with trials, it is a well-run trial. Safety is always critical, it is crucial and they have looked at that in an appropriate manner,” Margaret Harris told journalists in Geneva.
Asked to react to experimental COVID-19 vaccine use in China and Russia, she said: “The WHO would like to see vaccines go head to head so we can have clear information and to see these results against each other.”
AstraZeneca on Saturday said it had restarted its trial in Britain after regulators completed their review of a serious side effect in one trial participant there.
The vaccine being developed by Oxford and AstraZeneca is widely perceived to be one of the strongest contenders among the dozens of coronavirus vaccines in various stages of testing around the world.
The university said in large trials such as this “it is expected that some participants will become unwell and every case must be carefully evaluated to ensure careful assessment of safety.”
It said globally some 18,000 people have received its vaccine so far. Volunteers from some of the worst affected countries — Britain, Brazil, South Africa and the US — are taking part in the trial.
Although Oxford would not disclose information about the patient’s illness due to participant confidentiality, an AstraZeneca spokesman said earlier this week that a woman had developed severe neurological symptoms that prompted the pause. Specifically, the woman is said to have developed symptoms consistent with transverse myelitis, a rare inflammation of the spinal cord.
The university insisted that it is “committed to the safety of our participants and the highest standards of conduct in our studies and will continue to monitor safety closely.”
Pauses in drug trials are commonplace and the temporary hold led to a sharp fall in AstraZeneca’s share price following the announcement Tuesday.
The Oxford-AstraZeneca study had been previously stopped in July for several days after a participant developed neurological symptoms that turned out to be an undiagnosed case of multiple sclerosis that researchers said was unrelated to the vaccine.
During the third and final stage of testing, researchers look for any signs of possible side effects that may have gone undetected in earlier patient research. Because of their large size, the studies are considered the most important study phase for picking up less common side effects and establishing safety. The trials also assess effectiveness by tracking who gets sick and who doesn’t between patients getting the vaccine and those receiving a dummy shot.
Dr. Charlotte Summers, a lecturer in intensive care medicine at the University of Cambridge, said the pause was a sign that the Oxford team was putting safety issues first, but that it led to “much unhelpful speculation.”
Scientists and others around the world, including experts at the World Health Organization, have sought to keep a lid on expectations of an imminent breakthrough for coronavirus vaccines, stressing that vaccine trials are rarely straightforward.
Two other 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.