The participant who triggered a global shutdown of AstraZeneca’s Phase 3 Covid-19 vaccine trials was a woman in the United Kingdom who experienced neurological symptoms consistent with a rare but serious spinal inflammatory disorder called transverse myelitis, the drug maker’s chief executive, Pascal Soriot, said during a private conference call with investors on Wednesday morning.

The board tasked with overseeing the data and safety components of the AstraZeneca clinical trials confirmed that the participant was injected with the company’s Covid-19 vaccine and not a placebo.

“A vaccine that nobody wants to take is not very useful,” said Soriot.

On Wednesday, the company issued a statement, attributed to Soriot, saying AstraZeneca would be guided by a committee of independent experts in determining when to lift the hold on the trial “