Those concerned about the safety of a COVID-19 vaccine should feel reassured that AstraZeneca's phase 3 clinical trials were put on hold this week as investigators look into a potential side effect, Dr. Francis Collins, director of the National Institutes of Health, said Thursday.
"If anybody thinks we're just glossing over these kinds of issues in the big rush to approve a vaccine, this ought to be reassuring," Collins said during a "Doc to Doc" interview with NBC News medical correspondent Dr. John Torres, which was streamed on Facebook.
Collins said the pause in the trial showed that the researchers are taking safety seriously. It came after a study participant in the U.K. developed a neurological condition, reportedly an inflammation of the spinal cord. Investigators are now working to determine whether the event was caused by the vaccine or just a coincidence.
"You take any group of 30,000 people, and you watch them over the course of two or three months, it's likely somebody is going to have an illness that you didn't expect," Collins said. "And until you're sure that it was not connected to the trial, and you need to put it on clinical hold."
Testing sites in the U.S., which aim to enroll 30,000 people, were put on hold, as well as sites in Brazil and Europe.
Collins and other infectious disease experts have said it's not uncommon for clinical trials to pause because of unexpected adverse events.
During an online event Thursday morning, AstraZeneca's chief executive, Pascal Soriot, addressed public scrutiny of the clinical trial process.
"The difference with other vaccines trials is the whole world is not watching them," Soriot said. He added that it's possible the company will have adequate safety and efficacy data on the vaccine by the end of this year, as long as a monitoring committee allows the company to resume the trial.
Collins said that pausing the trial was the "ethical thing to do."
"You don't want to put anybody else at risk until you've sorted out the data."