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No doubt, the COVID-19 pandemic has prompted more than a few peers to ponder questions about immunity. Does SCI suppress my immune system? Does it make me more vulnerable to COVID, and should I be seeking booster vaccines earlier than the general public?”

The good news is that, at this point, there’s nothing to suggest that people with SCI are significantly more vulnerable to more serious outcomes or death due to COVID-19. So it seems like prudent advice to continue taking your usual precautions—masking in tight social or caregiving situations, and getting vaccines and boosters as recommended by the Provincial Health Officer.

However, evidence and statistics do make it clear that some people with SCI are at an elevated risk of developing often serious infections. For example, consider the abnormally-high number of people with SCI who contract life-threatening pneumonia. Some of this is because of the physiological complications of SCI. Skin breakdowns, impaired ability to breathe and cough, neurogenic bladder and catheter use, neurogenic bowel, extended hospitalizations, and limited physical activity levels all contribute to increased susceptibility to infection. But these only explain part of the problem.

Recently, many research groups around the globe have concluded that an SCI more directly inhibits the body’s ability to fight infections and viruses that gain entrance to the body. There’s even a name for it: SCI-induced immune deficiency syndrome, or SCI-IDS. At the moment, our understanding of SCI-IDS is limited, but work is being done on a number of fronts to learn more about the underlying mechanisms—and determine what some possible treatments might be, given that there are none at the moment.

There are dozens of research papers to sift through on the subject. Fortunately, two researchers at Drexel University in Philadelphia, Dr. Marisa Jeffries and Dr. Veronica Tom, have already done the heavy lifting. In the September 2021 issue of the journal Biology, Jeffries and Tom published a summary of research in the area with a paper titled Peripheral Immune Dysfunction: A Problem of Central Importance after Spinal Cord Injury.

In turn, we’ve made an in-house attempt to summarize their paper in plain language. Following are the takeaways that we believe are important.

First, there appear to be several consequences of SCI-IDS. It seems to result in a “persistent, low grade, peripheral inflammation” in a large number of people with SCI. In other words, many people with SCI have a continual low grade immune response in their bodies. As well, SCI-IDS increases susceptibility to serious infections. Finally, SCI-IDS appears to exacerbate many other secondary complications of SCI, including neuropathic pain, skin and bone deterioration, and cardiovascular disease.

Second, there appear to be several underlying mechanisms of SCI-IDS. The following mechanisms may be working by themselves or in tandem to suppress the immune system:

• SCI disrupts the ability of the central nervous system (CNS) to control the body’s most important immune organs, including the spleen, the adrenal glands, and lymph nodes. This effect seems to be worse as the level of injury rises, particularly above T6. Without control and coordination by the CNS, these organs do not work properly to create the necessary amount of infection- fighting cells.
• Research using animal models suggests that every bout of autonomic dysreflexia, or AD, contributes to SCI-IDS. AD triggers a release of hormones that suppress and even kill our infectionfighting immune cells. This appears to at least partially explain why immunity appears to become more compromised with higher level injuries, since the risk of AD increases with injury levels.
• Another mechanism of SCI-IDS appears to be dysfunction of the hypothalamic–pituitary–adrenal (HPA) axis, which is responsible for our body’s stress response. When SCI compromises our ability to tightly control the HPA axis, abnormally high amounts of corticosteroids are produced, which suppresses the immune system.
• Disrupted bone marrow functioning is also implicated in SCI-IDS. Bone marrow is vital for replenishing immune cells. SCI, especially higher levels, impairs bone marrow functioning.
• Obesity, which affects about 66 percent of people with SCI, is a big contributor to the persistent, low grade inflammation discussed above.
• Repetitive infections (ongoing UTIs or pressure ulcers, for example) are known to contribute to AD events, which are a major contributor to SCI-IDS.

Third, there are no approved therapies aimed at improving immune function for people with SCI. That’s why more research is needed. At the moment, the only thing that may improve immune function are certain types of exercise, which most people with SCI can do easily, without side effects. One promising avenue for improving immune function is limiting bouts of AD—for example, there is emerging evidence that electrical stimulation routines can stabilize blood pressure and interrupt dangerous bouts of hypertension during episodic AD.

It’s important to point out that our understanding of SCI-IDS is incomplete, as acknowledged by Jeffries and Toms in the conclusion of their paper:

“Immune changes post-SCI have major implications in the quality of life of SCI individuals as well as their treatment. With disruption of descending CNS input to immune organs as well as secondary complications of SCI contributing to SCIIDS, individuals with SCI are faced with a constant state of inflammation and increased risk of infection. Promisingly, recent preclinical research indicates a wide range of potential interventions that may be able to improve immune function and reduce the risk of infection. However, whether these effects are replicated after chronic immune dysfunction has already occurred, which populations of immune cells should be targeted, and how this affects immunity to various infection types in persons are all unknown facets of immune modulation post-SCI. Importantly, while there are many gaps in knowledge regarding immune function and modulation after SCI that remain to be filled, potential opportunities to identify effective therapeutics to better immune function will undoubtedly result in improved quality of life for those living with SCI.”

So what does one do with this information? The research into SCI’s effect on the immune system is in its early stages and much more work is needed before we can say definitively what the consequents of these possible effects are, if any. However, based on what is known so far, it may be wise to take a few precautionary measures to limit exposure to possible sources of infection and to adopt lifestyle behaviours that promote immune health. So, to repeat for emphasis, it may be best to err on the side of caution during the COVID pandemic and respiratory illness season by wearing masks in crowded spaces and keeping your immunizations up to date. Being physically active is important for your health and doing your best to avoid AD may maintain a stronger immune system. Keeping on top of signs of infection in order to catch or treat it early may also help stave off serious infections.