AstraZeneca Puts Hold On COVID-19 Test Vaccine After ‘Potentially Unexplained Illness’

The company stressed that such actions were routine in clinical trials and said an independent team would review safety data.

A potential COVID-19 vaccine being developed by AstraZeneca and the University of Oxford was put on hold Tuesday after a participant in a large-scale trial developed a “potentially unexplained illness.”

Stat News first reported that the Stage 3 trial had been temporarily paused after a serious adverse reaction in a volunteer. The New York Times later added that the participant was a part of a Phase 2/3 trial of the drug in Britain who developed a serious inflammatory syndrome that affects the spinal cord. It’s unclear how long the trial will be on hold.

“As part of the ongoing randomized, 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,” AstraZeneca said in a statement obtained by Stat News. “This is a routine action which has to happen whenever there is a potentially unexplained illness in one of the trials.”

The company said that illness can happen by chance in large trials and said it would expedite an independent review of singular events “to minimize any potential impact on the trial timeline.” The Stage 3 trial, which is expected to involve about 30,000 volunteers, is the last phase of testing before seeking approval and licensing. 

“We are committed to the safety of our participants and the highest standards of conduct in our trials,” AstraZeneca continued.

Stat added the participant is expected to recover, citing an unnamed source familiar with the case.

The vaccine candidate, known as AZD1222, was developed using chimpanzee adenovirus and is designed to induce a protective immune response that would guard against the coronavirus. Stat notes that this type of science has not been used before in an approved vaccine, but it has been tested in experimental treatments, including for the Ebola virus.

AstraZeneca’s vaccine is one of three currently in late-stage clinical trials in the United States and has been a leading contender in the race for a suitable treatment to COVID-19. The program began in August and is working toward enrolling up to 30,000 participants across 80 sites to determine the vaccine’s safety. It’s unclear what steps will be taken to pause the trials, although Stat notes it is common to stop recruiting volunteers or giving vaccine doses during such holds.

The Australian government had recently announced it secured nearly 34 million doses of the Oxford vaccine for local production should it prove successful. The U.S. government had also reserved about 300 million dose.

Two other drugs, from the pharmaceutical giants Pfizer and Moderna, are also in large-scale testing.

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