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Clinical trials of a vaccine against COVID-19 were interrupted

by Cédric Ayisa - September 18, 2020   1861 Views   5 min
Clinical trials of a vaccine against COVID-19 were interrupted


Clinical trials of a vaccine against COVID-19 were paused


Accurate (supported by evidence and facts; acceptable margin of error)

In an article by l’Agence France Presse dated September 10, 2020 and shared by the Canadian TVA news site, we could read that clinical trials of a vaccine against COVID-19 had been suspended. This statement is accurate.

The article reported that randomized trials by English pharmaceutical group AstraZeneca, in partnership with Oxford University, were halted on September 9, 2020 "after the appearance in a participant in the UK, of a 'potentially unexplained disease', possibly a serious side effect." The article also stated that AstraZeneca had retained independent experts to assess the situation and the condition of the participant and to identify whether testing should continue.

Announcing the pause

On September 9, in a press release, the pharmaceutical company AstraZeneca announced that it had "voluntarily halted" global trials of the AZD1222 vaccine. Trials for this vaccine, developed in collaboration with Oxford University, were suspended following an "unexplained illness" in a British participant. The information was confirmed by Oxford University. The University of Oxford emphasized that it is committed, along with AstraZeneca, to ensuring the safety of participants and the highest standards of conduct in their studies. The participant is no longer hospitalized. 

An independent committee was set up to analyze the data and determine whether the "unexplained illness" is vaccine-related. The company claimed that stopping the trials was a "routine action" in trials of this kind.

Why are pauses important in clinical trials?

As Dr. Soumya Swaminathan, Chief Scientist of the World Health Organization (WHO), explained at a press briefing (8'50" to 17'12"), in clinical trials, scientists are looking for both effectiveness and safety. Dr. Swaminathan said there are procedures to manage side effects in participants. She explained that "if it’s a mild side effect, there are things to be done. If it is major, as it was in this case, it is a serious side effect and therefore trial was halted".

The Chief Scientist described the pause as "normal procedure", "good clinical practice" and added that "it is a good thing, perhaps a warning sign or a lesson for everyone that there are ups and downs in research, ups and downs in clinical development and we have to be prepared for them".

The resumption of trials by AstraZeneca

On September 12, in a separate press release, AstraZeneca announced the resumption of trials in the United Kingdom, following the investigation of an independent committee and approval by the Medicines & Healthcare Products Regulatory Agency (MHRA), the authority that regulates drugs, medical devices and blood components for transfusion in the UK. The University of Oxford, where the vaccine was developed, said in a separate statement that the nature of the participant's illness cannot be revealed "for reasons of confidentiality". However, according to Stat News, AstraZeneca president Pascal Soriot is reported to have shared some details with investors. The participant in question is said to have experienced neurological symptoms related to a rare spinal cord disorder, transverse myelitis.

We can therefore conclude that Agence France Presse’s claim, which was republished by TVA, that the trials have been suspended is accurate. This pause was recorded globally on September 9. The UK trials resumed on September 12, three days after the temporary suspension of the trials.


Related to the incident. AstraZeneca began Phase 3 clinical trials in the U.S. on August 31. These trials are expected to enroll approximately 30,000 participants at 80 sites across the country, according to a statement from the National Institute of Health (NIH). Since September 9, the U.S. trials have been suspended. The NIH, in interviews with the media, says it is concerned. The NIH has launched its own investigation and has not yet decided to resume clinical trials of the vaccine in the United States.

In September, several media outlets also reported that in July 2020, a participant in the same U.K. clinical trials would have experienced similar side effects, but that these would have been caused by her underlying multiple sclerosis and not by the vaccine. No press release was issued by AstraZeneca at that time to inform the scientific community or the public of this incident.

Related to a delay in vaccine development. As noted above, stopping clinical trials because of adverse events is an essential and transparent practice in vaccine development to ensure the safety of trial participants and the safety of future vaccine recipients. However, especially in crises such as the one we are experiencing with the COVID-19 pandemic, each delay can cost many lives.

How many COVID-19 vaccines are presently being developed?

According to a document published by WHO on September 9, 2020, there are about 180 vaccines against COVID-19 in development worldwide. Of these, 35 are in clinical trials, nine of which are in Phase 3, the final stage of testing. In addition to the United Kingdom and the United States, AstraZeneca is also conducting Phase 2/3 or Phase 3 trials in Brazil and South Africa announced the NIH at the start of Phase 3 clinical trials. According to, a U.S. government directory, the trials currently paused in the United States, were taking place in 62 sites across the country.

What are the stages in clinical trials?

Normally, developing, testing, and approving a vaccine can take up to 10 years. There are three phases of human studies before a vaccine is approved for general use. But before reaching this stage, a vaccine must prove its effectiveness and then be tested in animals. Once the data have proven that the vaccine is safe and effective, the first tests on humans (volunteer participants) can begin.

Phases (According to BCCDC):

Phase 1: The vaccine is tested on 10 to 100 healthy, adult people to determine whether the vaccine is safe (without serious side effects), effective, and whether there is a relationship between the dose and side effects.

Phase 2: The vaccine is given to several hundred people (up to 500) who have characteristics (such as age and physical health) like those of the patients for whom the new vaccine is intended. Short-term side effects, dosage, and the timing of vaccine administration are examined.

Phase 3: The vaccine is administered to thousands of people (up to 30,000), as in the AstraZeneca/Oxford University AZD1222 trials in the United States. It is tested for efficacy and safety. In addition, recurrent side effects are investigated, and comparisons are made between those who received the vaccine and those who did not.

Once all phases of clinical trials are completed, the vaccine must meet the standards of the health authorities. In Canada, the Biologics and Radiopharmaceuticals Drugs Directorate (BMRD) of Health Canada approves the use of vaccines. After approval, the authorities continuously monitor the use of the vaccine to ensure its safety, efficacy and quality.

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  • September 23, 2020

    In an internal AstraZeneca report (not publicly available) obtained by CNN, it is explained that one trial participant, a 37-year-old woman living in the UK, "suffered from transverse myelitis", a rare neurological disease in which the spinal cord becomes inflamed. Information about this case had already been reported by several media outlets when the break in testing was announced. According to the report sent on 11 September to the scientists conducting AstraZeneca's vaccine trials, the woman had received her second dose of vaccine in late August. She was hospitalized on September 5, after "tripping (not falling)" while running. 

    According to the report, the researchers were sufficiently concerned about the situation to file a SUSAR (Suspected or Unexpected Serious Adverse Reaction) report. The report also explains that the neurologist who examined the participant "suggested that the symptoms were consistent with the diagnosis of transverse myelitis. AstraZeneca mentions twice in the report that the woman was diagnosed with "confirmed" transverse myelitis. 

    However, in a document updated on September 11 (available to the public), Oxford University refers only to participants who "developed unexplained neurological symptoms, such as a change in sensation or weakness of the limbs", which is consistent with the symptoms of the participant in question. It explains that the independent review concluded that "these illnesses were considered unlikely to be associated with the vaccine or that there was insufficient evidence to say with certainty that the illnesses were or were not related to the vaccine". At no time does Oxford University mention a case of transverse myelitis, emphasizing the confidentiality of patient information. 

    The announcement of the pause in AstraZeneca's testing on 8 September was seen as a signal of a willingness to comply with safety procedures. But when one looks closer, AstraZeneca's transparency can be questioned. 

    On the question of transparency, on September 8, the CEOs of nine biopharmaceutical companies, including AstraZeneca, signed the "We Stand With Science" pledge to demonstrate their commitment to develop and test potential COVID-19 vaccines according to high ethical standards and rigorous scientific principles. 

    But the pledge also represents a way for the pharmaceutical industry to respond to public fears (especially in the United States), given that 62 percent of adults in the United States fear that "political pressure from the Trump administration will cause the FDA to rush to approve a COVID-19 vaccine without ensuring that it is safe and effective.”  

    According to the Mayo Clinic, transverse myelitis is an inflammation on both sides of a section of the spinal cord. This neurological disorder often damages the insulating material that covers nerve cell fibers (myelin). 

    Transverse myelitis interrupts the messages that nerves in the spinal cord send throughout the body. This can lead to pain, muscle weakness, paralysis, sensory problems or dysfunction of the bladder and intestines. 


Oxford University

World health organization (WHO)

Stat News

Clinical Trials

Kaiser Health News

National Institute of Health

Biologic and Radiopharmaceutical Drugs Directorate

Centers for Disease Control (CDC)



Immunize BC




Oxford University 

Mayo Clinic,nerves%20send%20throughout%20the%20body 

Kaiser Family Foundation 

New York Times 



TVA Nouvelles

Clinical trials of a vaccine against COVID-19 were paused


Accurate (supported by evidence and facts; acceptable margin of error)

 September 18, 2020


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