The pharmaceutical company AstraZeneca has halted the late stage trial for a COVID-19 vaccine this week due to a suspected adverse reaction in a participant.

Medical ethicist Arthur Caplan told Boston Public Radio on Wednesday the participant developed an inflammation of the spinal cord and had to be hospitalized, causing the company to pause the trial in order to conduct a safety review and determine whether the reaction was in fact caused by the vaccine.

Caplan said the takeaway from this latest development is that medical trials cannot be rushed, no matter the astrazeneca-vaccine-safety.html">political pressure to quickly develop a vaccine.

“We want to vaccinate our way out of this thing and people keep spinning tales it’ll be here in October,” he said. “I keep saying no it wont, it’ll be here next year, and I don’t know when, but maybe the end of the year … because you’ve got to collect this data.”

Art Caplan is the Drs. William F. and Virginia Connolly Mitty chair and the director of the division of medical ethics at the NYU Grossman School of Medicine.