The participant who triggered a global shutdown of AstraZeneca’s Phase 3 Covid-19 vaccine trials was a woman in the United Kingdom who experienced neurological symptoms consistent with a rare but serious spinal inflammatory disorder called transverse myelitis, the drug maker’s chief executive, Pascal Soriot, said during a private conference call with investors on Wednesday morning.

The woman’s diagnosis has not been confirmed yet, but she is improving and will likely be discharged from the hospital as early as Wednesday, Soriot said.

The board tasked with overseeing the data and safety components of the AstraZeneca clinical trials confirmed that the participant was injected with the company’s Covid-19 vaccine and not a placebo, Soriot said on the conference call, which was set up by the investment bank J.P. Morgan.


Soriot also confirmed that the clinical trial was halted once previously in July after a participant experienced neurological symptoms. Upon further examination, that participant was diagnosed with multiple sclerosis, deemed to be unrelated to the Covid-19 vaccine treatment, he said.

The new disclosures made by Soriot were heard by three investors participating on the call and were shared with STAT. An AstraZeneca spokesperson did not respond to an email request for further comment.


One investor on the call said Soriot’s comments were intended to reassure investors that the company was taking the possible vaccine safety event seriously, and to reverse any damage to the company’s stock price. “A vaccine that nobody wants to take is not very useful,” said Soriot.

To date, AstraZeneca’s public statements on the pause have been sparse with details. For instance, the company has not publicly confirmed that this is the second time its trials have been stopped to investigate health events among participants.

On Wednesday, the company issued a statement, attributed to Soriot, saying AstraZeneca would be guided by a committee of independent experts in determining when to lift the hold on the trial “so that we can continue our work at the earliest opportunity to provide this vaccine broadly, equitably and at no profit during this pandemic.”

AstraZeneca’s is the first Phase 3 Covid-19 vaccine trial known to have been put on hold. Such holds are not uncommon, and it’s not clear yet how long AstraZeneca’s will last.

“To have a clinical hold, as has been placed on AstraZeneca as of yesterday, because of a single serious adverse event is not at all unprecedented,” Francis Collins, the director of the National Institutes of Health, told a Senate panel on Wednesday. “This certainly happens in any large-scale trial where you have tens of thousands of people invested in taking part, some of them may get ill and you always have to try to figure out: Is that because of the vaccine, or were they going to get that illness anyway?”

AstraZeneca only began its Phase 3 trial in the U.S. in late August. The U.S. trial is currently taking place at 62 sites across the country, according to, a government registry, though some have not yet started enrolling participants. The Phase 3 trial in the U.S. aims to enroll about 30,000 participants at 80 sites across the country, according to a release last week from the NIH. Phase 2/3 trials were previously started in the U.K., Brazil, and South Africa.

The vaccine — known as AZD1222 — uses an adenovirus that carries a gene for one of the proteins in SARS-CoV-2, the virus that causes Covid-19. The adenovirus is designed to induce the immune system to generate a protective response against SARS-2. The platform has not been used in an approved vaccine, but has been tested in experimental vaccines against other viruses, including the Ebola virus.

Transverse myelitis is a serious condition involving inflammation of the spinal cord that can cause muscle weakness, paralysis, pain and bladder problems. In rare instances, vaccines have triggered cases of transverse myelitis; although it can also be caused by viral infections.

Helen Branswell and Lev Facher contributed reporting. 

  • I thought the AstraZenica vaccine was really the Oxford developed vaccine and that AstraZenica was only involved in financing, organizing trials, mass manufacturing, and distribution. I thought the Oxford vaccine was the ONLY one that caused the creation of T-cells (in addition to antibodies) that actually seek out the covid19 virus and kill it. The others are messenger RNA TYPE (Moderna, Pfizer) and do NOT produce T-cells. However, based on your reporting, this is NOT the Oxford University developed vaccine but is an AstraZenica developed vaccine. So, either your reporting is shoddy and misrepresents the truth, or the Oxford University vaccine is no longer being worked on.

    • This is how it usually goes. Big Pharma don’t do all the research, they buy molecules that Biotech Companies and Universities develop and test (either in collaboration or by themselves). So Oxford Univ developed the vaccine (usually underpaid post-docs, but I’m not going to go there) and did pre-clinical trials. If they results are successful they present them to a Pharma Company (Astra Zeneca in this case) that buys the product and starts the actual Clinical trials (Phases 1 to 4).
      Ok, just to be clear, no vaccine is producing T cells. What most of them are doing (either with Adenovirus or mRNA) is making the host’s cells (subject injected) to produce a fragment of the virus, then the host T-cells will recognize that as a threat and start the immune reaction that will lead to Antibody (early phase protection, then they get clear out the body) and memory cells (long term protection) production.

      I hope this helps

  • It’s the adjuvants that are used in the vaccine that cause most if not all adverse events associated with vaccine. Their purpose is to cause a reaction within the adaptive immune system, so that it will mount a defense against the disease it’s meant to treat. This causes inflammation as does most anything else that is unfamiliar and or traumatic to our bodies. Inflammation is an expected result of vaccination. So why stop the trial. It’s likely that this person has an undiagnosed autoimmune disorder. Or Lyme disease. And should not be receiving vaccinations at all. Delay, delay, delay. And for what?

  • Felipe said…..Scientists all around the world have said numerous times that existing drugs and treatment cures it.

    WHICH ONE???

  • This swine flu vaccine of 1976 cards 400 cases of Gbs or guillane barre out of 40 million vacvine but saved hundreds of thousands of lives so it’s worth the risk and the trial should continue

    • Who is the judge of the worth of the risk? If they renamed Guillain-Barre Syndrome to “Christopher Reeve Syndrome” or something else that is easy to say, and before each swine flu injection, the recipient was informed there’s a 1 in 100,000 chance they will never be able to walk again, is that worth the risk? Sure, from a pure numbers game, there’s an enormous net lives saved in this example, but “risk worthiness” should an individual decision and not hidden like they do in countries run without a Constitution like China and Russia. An informed individual right does not change the ability to achieve herd immunity in a democratic country, if there is adequate safety data.

    • Right? Seems like they would have medically screened their trial participants for multiple reasons, and certainly a vaccine wouldn’t cause such injury. Yet, vaccines cause such injury. Funny how many giant red flags obscenely wave as we’re told they’re green and the weak sheep rally behind. No matter how big a joke the government/big pharma is American citizens are the ones being laughed at the hardest. Now everyone line up for the gas chamber…err, free shots. Brain. Dead. More, please.

  • For 95% of the population there is no need for a covid-19 vaccine. Scientists all around the world have said numerous times that existing drugs and treatment cures it. Also, the virus is nowhere near as aggressive and contagious as the WHO said. New Study but UCLA just came out confirming this.

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