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With growing concern for the coronavirus pandemic and potential treatment modalities, modifiable risk factors have been identified that may allow the public to take part in protecting themselves from future infection. One of which is the presumed link between vitamin D deficiency and worsening of COVID-19 outcomes. Data show a possible link between patients with a vitamin D deficiency and symptom severity with COVID-19 infections.  While a vaccine is hopeful in the future, it is prudent to investigate ways to safeguard the immune systems through manageable risk factors, such as vitamin D insufficiency, in the interim. 

While the exact link between vitamin D deficiency and infection is unknown, it has been demonstrated that vitamin D effects the immune system. The active form of vitamin D (calcitriol) has been studied in numerous lung-related diseases and infections such as upper respiratory infections, asthma, COPD and even tuberculosis. The function of vitamin D in the immunologic response involves suppressing the acquired immune system through dendritic cell inhibition. Dendritic cells are antigen-presenting cells, meaning they process the material viral antigens possess and display this information on cell surfaces. Certain cells (specifically T cells) respond to this information and enact an immune response to the foreign invader (i.e. a pathogen, allergen or potential tumor). When vitamin D effectively stunts dendritic cell maturation the body is not able to produce an overactive response to a pathogen, thereby diminishing the latent effects of an infection such as COVID-19. Infections such as COVID-19 cause more damage when the immune system over responds with inflammation (e.g., cytokine release). Data suggests vitamin D acts as an anti-inflammatory agent and protects the body from such dangerous inflammatory processes. 
 
Some studies have yielded inconclusive results about how vitamin D levels and infection rates correlate. However, benefits from supplementation have been seen in patients with severe deficits (less than 10ng/mL). Standard vitamin D levels generally range from 20-50 ng/mL. When levels fall below 20 ng/mL, increased risk and severity of symptoms can result.  
 
Although little is known about future treatments for the coronavirus, there may be potential benefit from supplementing vitamin D levels in patients who are deficient upon admission to a hospital. According to Dr. Ben Thrower, medical director of the MS Institute at the Shepherd Center in Atlanta, vitamin D has been shown to positively affect clinical outcomes in patients with other pro-inflammatory conditions, such as MS. Low vitamin D levels are considered a risk factor for developing MS and therefore seen as a modifiable element to prevent this disease. Data suggests patients with MS who have vitamin D levels less than 20ng/mL have double the risk of developing MS later in life. 

The primary source of vitamin D for the general population is regular sun exposure, but it is also available in certain foods and supplements. Dietary sources of vitamin D include eggs, fatty fish, and fortified dairy products and cereals. Vitamin D is available in both single supplements and multivitamin formulations. The recommended dietary allowance for vitamin D in most adults is 15 mcg per day or 600 international units. Unlike certain other vitamins, vitamin D is fat-soluble, which means it is readily stored in the body for long periods of time and can accumulate when taken in excess. Dr. Thrower went on to explain that it is rare to experience toxic vitamin D levels when the diet is the primary source; however, overdoses can occur when supplements are taken improperly.  For this reason, Dr. Thrower suggests patients should discuss with their MS provider before starting any new supplements, including vitamin D, to determine if medication interactions or other health issues may exist. 
 
No studies currently evaluate the relationship between vitamin D supplementation in MS patients with COVID, but there have been noteworthy recommendations published about MS treatment during the pandemic. Given the consequential immunosuppression linked with some MS treatment regimens, concerned patients should speak with their MS providers to understand if they are at higher risk for acquiring coronavirus infection. With that in mind, concerns have been raised as to the tradeoffs of continuing such agents during the pandemic. MS neurologists, such as Dr. Thrower, cautioned that patients need to understand the risks versus benefits of disease-modifying regimens; because stopping treatment could result in disease progression. Special considerations for changing or discontinuing certain therapies may be given to patients with additional risk factors such as age (65 and older), disease course, state of disability, and specific drug factors, to name a few. 
 
To ease some distress, it is believed that MS patients are similar to the vast majority of the general public; most patients who get COVID-19 will only experience mild symptoms. Patients concerned about their MS treatment regimen during this pandemic should discuss their concerns with their MS providers. Otherwise, following general COVID-19 guidelines from the CDC and WHO is essential to help prevent exposure to the virus. Specific recommendations include: washing hands with soap and water for 20 seconds or at least a 60 percent alcohol-based hand sanitizer, social distancing (6 foot distancing and avoiding crowds of 10 or more), wearing a face mask in public when possible, covering your mouth with a tissue or the inside of your elbow when sneezing, and avoiding excessive face touching when in public. As with any illness, continue monitoring your health and remain vigilant to any new symptoms (fever, cough, shortness of breath, loss of smell or taste) that may alert you of an early sign of potential infection.

MS and COVID-19

Given the fluidity of the pandemic, and the limited knowledge about patients with MS and COVID-19, it is crucial to promote ongoing documentation to discover potential risk factors that are unique to patients with MS and other CNS demyelinating diseases. COViMS (COVID-19 infections in MS and Related Diseases) has recently been launched as a joint effort of the National MS Society, Consortium of MS Centers and Multiple Sclerosis Society of Canada to record information from patients with MS who have tested positive for COVID-19 to determine if there are associated factors between disease-modifying therapies and clinical outcomes post-infection. As data continues to expand, we will hopefully gain a better understanding of how to best support patients with MS during these critical times.