Vaccine trial halted after participant has possible adverse reaction

AstraZeneca on Tuesday temporarily halted its phase three trial of a possible coronavirus vaccine after one participant may have suffered from a serious adverse reaction. The potential vaccine was created by the pharmaceutical giant along with Oxford University and is being tested in both the U.K. and the U.S.

"As part of the ongoing randomised, controlled global trials of the Oxford coronavirus vaccine, our standard review process was triggered and we voluntarily paused vaccination to allow review of safety data by an independent committee," a spokesperson for AstraZeneca said. "This is a routine action which has to happen whenever there is a potentially unexplained illness in one of the trials, while it is investigated, ensuring we maintain the integrity of the trials."

AstraZeneca did not provide details on what type of reaction the participant may have suffered or when the trial is expected to resume. The spokesperson stated they are expediting the review in hopes that it will not cause any drastic delays.

Dr. Mohamed Slaoui, the chief adviser to Operation Warp Speed, told CBS News that the U.K.'s trial Data Safety Monitoring Board is "conducting an in-depth review of the company's vaccine candidate which is standard procedure when an adverse event occurs in clinical trials."

Dr. Jeff Pothoff, chief quality officer of University of Wisconsin Health, where one of the trials is being conducted, received the potential vaccine Wednesday, CBS affiliate WISC-TV reports. He noted that it's not unusual for trials to be paused.

"We don't know much more at this point. All these groups — AstraZeneca, Pfizer and Moderna — they have incredible attention to safety so if there is any whisper or wisp of something that would've gone wrong, or sometimes it's just related to regulatory issues," Pothoff said. "There's so much paperwork, and the i's dotted and t's crossed that they would stop the trial temporarily while they figure something out."

UW Health has temporarily paused enrollment in the vaccine trial and canceled all upcoming appointments while the trial remains on hold, WISC reports.

The Oxford vaccine is one of the leading candidates in the race to develop an effective vaccine for COVID-19. Oxford University has been conducting phase three trials in the U.K., Brazil and South Africa. In earlier phases, no evidence indicated the vaccine caused serious reactions.

Other candidates in phase three of testing are being developed by Pfizer/BioNtech and Moderna. Russia skipped phase three testing of its potential vaccine. On Tuesday, the CEOs of nine drugmakers — AstraZeneca, BioNTech, GlaxoSmithKline, Johnson & Johnson, Merck, Moderna, Novavax, Pfizer and Sanofi — released a joint statement vowing not to release any vaccine unless proven safe by rigorous testing.

President Trump has claimed a vaccine could be ready as early as November, but his own health experts say that timeline is highly unlikely.