Late-stage studies of AstraZeneca’s COVID-19 vaccine candidate are on temporary hold while the company investigates whether a patient suffered a serious side effect or if the illness had nothing to do with the shot.
In a statement issued Tuesday evening, the company said its “standard review process triggered a pause to vaccination to allow review of safety data.”
AstraZeneca didn’t reveal any information about the possible side effect except to call it “a potentially unexplained illness.”
The health news site STAT first reported the pause in testing, saying the possible side effect occurred in the United Kingdom.
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. Those two vaccines work differently than AstraZeneca’s, and the studies already have recruited about two-thirds of the needed volunteers.
Temporary holds of large medical studies aren’t unusual, and investigating any serious or unexpected reaction is a mandatory part of safety testing. AstraZeneca pointed out that it’s possible the problem could be a coincidence; illnesses of all sorts could arise in studies of thousands of people.