AstraZeneca, Oxford COVID-19 Vaccine Trial Put on Hold for Safety Concern

Clinical assessment of the coronavirus 2019 (COVID-19) vaccine candidate developed by AstraZeneca and the University of Oxford has been put on hold due to a suspected serious adverse event reaction in a UK-based participant, according to a new report from STAT News.

The report comes one week into the launch of a phase 3 trial gauging AZD1222 in up to 30,000 US adults. The federally-backed program Operation Warp Speed is contributing funds toward the phase 3 program. Another series of countries—including Mexico, Argentina, and Australia—have entered agreements with the company for the mass production of AZD1222 doses for its residents.

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An AstraZeneca spokesperson said in a statement that the investigation’s pause is the result of a routine action required to occur “whenever there is a potentially unexplained illness in one of the trials.” As such, the company is now looking to expedite the review of the single event to “minimize any potential impact on the trial timeline.”

As posed by the report, whichever agency placed a hold on the trial—be it AstraZeneca, the university’s investigators, or a regulatory—is not immediately certain. An unnamed source who spoke with the publication stated the observed participant is expected to recover from the undisclosed adverse event.

AZD1222 was co-invented by the University of Oxford and its spin-out company, Vaccitech. It uses a replication-deficient chimpanzee viral vector based on a weakened version of an adenovirus that causes infections in chimpanzees and contains the genetic material of the SARS-CoV-2 virus spike protein.

In July, the pharmaceutical company reported interim results from their ongoing phase 1/2 trial showing AZD1222 was generally tolerable, and generated robust immune responses against the SARS-CoV-2 virus in all evaluated participants.

On Tuesday morning, AstraZeneca was among 9 pharmaceutical companies to sign a letter pledging the continued assurance and monitoring for safety and tolerability in the first COVID-19 vaccine candidates, in response to reports that a vaccine may be regulated and distributed in alignment with the upcoming US Presidential Eleciton in November.