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A major COVID-19 vaccine developer just hit a huge stumbling block, temporarily halts studies

astrazeneca vaccine coronavirus
Photo via Jernej Furman/Flickr (CC BY 2.0)

One potential COVID-19 vaccine-maker paused global trials after one volunteer experienced a severe adverse reaction. The stumbling block is a reminder of the importance of large-scale testing and that no potential coronavirus solution, even an AstraZeneca vaccine that had seemed to hold promise, is a sure thing until it finishes all of its clinical trials. 

On Sept. 8, British-Swedish company AstraZeneca and the University of Oxford announced they were putting phase 3 trials on hold after a U.K. volunteer developed an inflammatory syndrome called transverse myelitis. The New York Times reported viral infections often spark the syndrome, which is an inflammation of the spinal cord. 

An anonymous source told the Times that it’s still unclear whether the diagnosis is linked to the vaccine. According to STAT News, an AstraZeneca spokesperson said in a statement that this was a standard response during vaccine development. 

“As part of the ongoing randomized, controlled global trials of the Oxford coronavirus vaccine, our stand review process was triggered, and we voluntarily paused vaccination to allow review of safety data by an independent committee,” the spokesperson 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.” 

Phase 3 trials exist in vaccine development for this very reason. In a phase 3 trial, the vaccine is given to thousands of participants to test its efficacy and to see if any harmful side effects emerge that were not caught in the phase 2 trial, which only involves hundreds of volunteers. 

Dr. Anthony Fauci, the National Institute of Allergy and Infectious Diseases director, told CBS This Morning that pausing the global trials was not an unusual safety precaution taken during vaccine development. 

“It’s really one of the safety valves that you have on clinical trials such as this, so it’s unfortunate that it happened,” Fauci said. “Hopefully, they’ll work it out and be able to proceed along with the remainder of the trial but you don’t know. They need to investigate it further.”

In its vaccine tracker, the Times reported that AstraZeneca’s vaccine is based on a chimpanzee adenovirus called ChAdOx1. STAT News explained that the vaccine “uses an adenovirus that carries a gene for one of the proteins in SARS-CoV-2.” The adenovirus provokes the immune system to generate a protective response against the virus.

The U.S. government gave the developers $1.2 billion in May. In August, the company began phase 3 trials in the U.S. AstraZeneca recently said the company could start delivering emergency vaccines as early as October.

There are two other companies with vaccines in phase 3 trials in the U.S.: Moderna and BioNTech. Both are genetic vaccines that work very differently from the AstraZeneca vaccine, a viral vector vaccine. 

The AstraZeneca vaccine is actually more similar to the vaccines developed by Russia and China, approved for limited use before they even completed phase 3 trials. They are also viral vector vaccines that use adenoviruses to inoculate patients. 

By Sept. 12, though, the AstraZeneca trials had begun again.

Read more on the coronavirus vaccine:

Sources: New York Times, STAT News, Reuters


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