Skip to Main Content

A large, United Kingdom-based Phase 2/3 study testing a Covid-19 vaccine being developed by AstraZeneca has been restarted, according to a statement from the company. News that the trial is resuming comes four days after the disclosure that it had been paused because of a suspected serious adverse reaction in a participant.

A spokesperson for AstraZeneca told STAT that at this point, only the trial in the U.K. has been resumed. The company is also conducting Phase 2/3 or Phase 3 trials in the U.S. and Brazil, as well as a Phase 1/2 trial in South Africa.


“The Company will continue to work with health authorities across the world and be guided as to when other clinical trials can resume to provide the vaccine broadly, equitably and at no profit during this pandemic,” the spokesperson, Michele Meixell, wrote in an email.

Saturday’s statement from AstraZeneca said the independent U.K. investigation into the event has concluded and it advised the Medicines Health Regulatory Authority, Britain’s equivalent of the Food and Drug Administration, that it was safe to resume the trial. The MHRA concurred and gave the green light for the trial to restart.

The illness that triggered the international pause, which occurred in a woman who was in the vaccine arm of the U.K. trial, has not been officially disclosed, though AstraZeneca CEO Pascal Soriot told a group of investors on Wednesday that her symptoms were consistent with transverse myelitis, a serious condition involving inflammation of the spinal cord that can cause muscle weakness, paralysis, pain and bladder problems.


The AstraZeneca statement said information about the illness the woman suffered cannot be disclosed. Oxford University, where the vaccine was developed, said in a separate statement that the nature of the illness cannot be revealed “for reasons of participant confidentiality.”

As part of the review process, independent boards overseeing trials of a number of other Covid-19 vaccines were analyzing their own data, looking for cases. There are at least 35 vaccines in clinical trials around the world, nine of which are in Phase 3, the final stage of testing.

It’s not uncommon for clinical trials to be paused. This is the second known hold of studies of the AstraZeneca vaccine. A woman in the U.K. trial was diagnosed with multiple sclerosis in July, but that event, which triggered the first pause, was deemed not to be related to the vaccine.

An AstraZeneca spokesperson previously described the decision as a “routine action which has to happen whenever there is a potentially unexplained illness” in a trial. Still, the pause drew extraordinary attention because of the urgent need for progress on Covid-19 vaccines in the midst of the pandemic.

Correction: An earlier version of this story misstated the stage of the AstraZeneca trial in South Africa. It is a Phase 1/2 trial. 

  • All well and good that the trial can resume and hopefully in all countries, but the occurrence of a rare event highlights the need for continued studies after initial approval. Post-marketing registries should be mandatory for all approved coronavirus vaccines enrolling about one-million patients. Minimal data collection should be required and subject participation voluntary. A 6 month observational window for unusual outcomes could suffice to confirm the established safety and efficacy of the vaccines. A single data collection center for all approved vaccines could permit comparisons of the safety and effectiveness among them.

  • Disappointed with the explanations especially under the cover of participant confidentiality.
    The world citizens have the rights to know more details about this unique case to arrive at their own judgment.

  • I find it ironic that when people die of COVID but they have comorbidities it is classified as a Covid death – however if someone gets a serious illness when they have a vaccine it is usually classed as not related.

  • Bloody disgusting that everything is deemed to be OK & its all ‘safe to resume trials’- nothing to see here, MS not related, ‘participant confidentiality’, ‘MHRA concurred’. If the bloody covert vaccine is so good, why not accept liability for future harm?? Unbelievable.

  • Transverse myelities is SO much worse then what is being said in the media. My husband has had it for 5 yrs and was paralyzed from mid chest down. He has to learn how to walk again, use his hand and arm and his bodily functions. Some people are paralyzed from their neck down and are vented and never leave a bed again. Please due your research on this as people DO get TM from vaccinations.

    • Transverse myelitis does look bad, no doubt. It seems plausible that vaccines could cause it, but based on the Mayo Clinic’s transverse myelitis web page the evidence is inconclusive. Although the exact cause is not known, some viruses and bacterial infections are associated with the condition. This suggests to me that if you skip the vaccine hoping to avoid transverse myelitis you still could acquire it if you catch the virus.

Comments are closed.