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# AstraZeneca Covid-19 Trial Stops Over Safety Signal
- URL: https://www.fdaweb.com/astrazeneca-covid-19-trial-stops-over-safety-signal/
- Published: 2020-09-08T12:00:00.000Z
- Updated: 2026-09-14T16:27:50.000Z
- Author: David McFarland
- Tags: Biologics, #legacy-id-D5147608

As public confidence wanes on potential Covid-19 vaccines, an AstraZeneca and University of Oxford Phase 3 vaccine [study](https://clinicaltrials.gov/ct2/show/NCT04516746?ref=fdaweb.com) has been put on clinical hold due to a serious adverse reaction in a trial participant in the United Kingdom. It is not determined whether FDA or another regulatory agency ordered the hold or if it was a precautionary and voluntary action by AstraZeneca, according to [Stat News](https://www.statnews.com/2020/09/08/astrazeneca-covid-19-vaccine-study-put-on-hold-due-to-suspected-adverse-reaction-in-participant-in-the-u-k/?ref=fdaweb.com).  

An AstraZeneca spokesperson said in a statement that the company’s “standard review process triggered a pause to vaccination to allow review of safety data.” Details about the adverse reaction were not shared, although the trial participant is expected to recover, Stat reports.

An individual familiar with the adverse reaction told Stat that it is having an impact on other AstraZeneca vaccine trials underway and clinical trials being conducted by other vaccine manufacturers. Researchers conducting other trials are now combing for similar cases in databases reviewed by data and safety monitoring boards, the individual said.

AstraZeneca began the Phase 3 trial in the U.S. in late August. In total, there are 62 sites across the country, according to the clinicaltrials.gov database.