More on the adverse reaction that stopped AstraZeneca’s COVID-19 vaccine trial

Several sources have now reported that the illness that stopped AstraZeneca’s COVID-19 vaccine clinical trial was a case of transverse myelitis. This is an inflammation of the spinal cord that can be associated with disruption of nerve function. In the most severe cases this can lead to partial or complete paralysis and is therefore a very serious problem. 

Despite this, Pascal Soriot, AstraZeneca’s CEO, said in a phone call reported by STAT, “the subject had serious neurological problems, but that there is no final diagnosis and that there will not be one until more tests are carried out. Those tests will be delivered to an independent safety committee that will review the event and establish a final diagnosis.”

There has been suspicion that vaccines might be able to trigger transverse myelitis, in particular Hepatitis B vaccine and childhood vaccines such as measles, mumps, rubella, and diphtheria.  

Several vaccines, including the flu vaccine, have been tied to other autoimmune disorders, including Guillain-Barre syndrome. While these complications are rare, the common factor in all of these diseases is that the immune system attacks the nerves. 

How might a vaccine cause the immune system to attack the nerves in the body? By stimulating an immune response to foreign proteins, the vaccine could accidentally stimulate an immune response that cross reacts 2 proteins and the nervous system. This cross reaction could lead to inflammation in the nervous system that can cause the inflammation seen in this patient.

However, other sources of inflammation such as autoimmune disease could also cause this reaction, or the autoimmune disease could be made more prominent because of the immune stimulation from the vaccine. This cross-reacting inflammation might be more prominent with the AstraZeneca vaccine because it contains whole, live chimpanzee virus. 

Complicating the cause of this reaction, both transverse myelitis and Guillain-Barre syndrome have been identified as possible complications of Covid-19. Therefore, It is possible that an immune response to COVID-19 proteins themselves may lead to these neurological complications. This means these competing complications will have to be monitored closely in all vaccine trials. 

As I have previously documented in this blog, there were significant side effects in the initial clinical trials of this vaccine including fevers and muscle aches. None were documented as serious. However, according to a report in Nature News, a subject in the Phase I/II trial developed symptoms of transverse myelitis in July. That trial was also stopped, but this information was not reported because the subject was diagnosed with an “unrelated neurological illness.” This was identified as multiple sclerosis, and after a safety review, trials resumed. Ms. Michele Meixell, a company spokesperson, confirmed the initial trial pause, saying that the “independent review panel concluded this illness was unrelated to the vaccine.”

In retrospect, given the current case of neurological disease, could the illness in the prior trial have been initiated or worsened by the vaccine? None of this is clear and awaits the independent board review. 

Going forward, even if these illnesses are not related specifically to the vaccine, there needs to be careful monitoring for neurological side effects in COVID-19 vaccine trials.

On the other hand, if the neurological illnesses are found to be related to this vaccine, it creates a use risk that needs to be evaluated for each individual who is a potential recipient.  If this is the case, we can only hope that other vaccines in development won’t have these issues.

Published by jbakerjrblog

Immunologist, former Army MD, former head of allergy and clinical immunology at University of Michigan, vaccine developer and opinionated guy.

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