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Do Links Between the Immune System Response to Concussions and COVID-19 Shed Light on Future Therapy?

As millions receive the COVID-19 vaccines, multiple reports have arisen about people experiencing a range of side effects – most commonly – fever, fatigue, headache, and nausea.

There have been reports of less common side effects –neurological and otherwise —  that suggest a link between post-concussion syndrome and the immune system response to COVID.

A patient reported suffering from post-concussion syndrome (PCS) for months following a brain injury; which included persistent cognitive issues and brain fog. However, after receiving their first dose of the Moderna vaccine, their symptoms seemed to improve over the next few days, feeling “the best [they had ever felt] since [their] most recent concussion a few months back”1

So how could a vaccine for a viral infection help alleviate a physically induced cognitive impairment? 

Dr. Akiko Iwasaki, professor of immunology at Yale University – speculates that persistent symptoms suffered by COVID-19 “long haulers” could be explained by one or a combination of reasons; fragments of the virus that remain after infection; and a heightened immune response to the infection that results in healthy tissue being targeted2

A study has shown that a severe inflammatory response can occur in the brain tissue of those with COVID-19. Researchers from the Freiburg University Medical Center saw an increase in immune cells of the brain, called microglial cells, which become strongly activated in the brain, causing inflammation to the brainstem3. This disruption in the brain’s immune response could contribute to the neurological symptoms some COVID patients face. Fortunately, a study conducted by an advocacy group called LongCovidSOS found that 56.7% of people experienced an improvement in long COVID symptoms one week after receiving their first dose of the vaccination4.

Similarly, a concussion or brain injury could cause a cellular cascade that results in the immune system overreacting and attacking the brain, says Jeffrey Bazarian, a physician at the University of Rochester Medical Center5 – this response ultimately leads to cognitive dysfunction and emotional distress as well6

So, PCS and long COVID could be explained by a hyperactive immune response, which causes the persistent symptoms these patients face – how does the vaccine help? It seems that the vaccine helps reset the immune system, allowing the body to understand that it should not attack itself but rather focus its energy into creating antibodies to help fight infection2. When the immune system stops attacking healthy tissue, normal cognitive and neurological function restores. 

With PCS, we can hypothesize that the vaccine did the exact same thing with the long COVID patients – it resets the immune system to allocate its resources into creating antibodies instead of targeting the brain. This explains why the patient felt relief from their symptoms after receiving their vaccine. Unfortunately, the vaccine was not a long-term solution as they had a relapse of PCS symptoms soon after1

So, what could be a long-term solution? Dr. Marco Prinz from the Institute of Neuropathology at Freiburg University Medical Center says that immunosuppressive treatment could help reduce inflammation and restore proper functioning in COVID patients. 

The same has been said for brain injuries, where Dr. Bazarian sees prospects in a pill or vaccine that can block a hyperactive immune response5.  On the downside, immunosuppressants increase a patient’s risk of infection.

More research and investment in understanding the mechanisms at play and the relationship between COVID-19 and the brain are needed to improve our knowledge about how the brain reacts to both viral infection and physical injuries.


1Chem__Tester. “r/Concussion – Post-Concussion Syndrome Alleviated by Covid Vaccine – Anyone Else?” reddit, May 5, 2021. 

2“Long Covid Symptoms Ease after Vaccination, Survey Finds.” The Guardian. Guardian News and Media, May 18, 2021. 

3staff, Science X. “COVID-19 Can Cause Severe Inflammation in the Brain.” Medical Xpress – medical research advances and health news. Medical Xpress, June 14, 2021. 

4Scribner, Herb. “Does the Vaccine Ease Long COVID-19 Symptoms?” Deseret News. Deseret News, May 19, 2021. 

5Posted March 10. “Immune System Compromised after a Concussion: Pills May Be in the Making as a Cure.” Concussion Management of New York. Accessed June 17, 2021. 

6Verboon, Laura N., Hiren C. Patel, and Andrew D. Greenhalgh. “The Immune System’s Role in the Consequences of Mild Traumatic Brain Injury (Concussion).” Frontiers in Immunology 12 (2021).