Based on the clinical presentations, treatments, and outcomes of COVID-19, in this study, we were able to demonstrate that COVID-19 affects individuals with SPSD in a similar way that it affects the general population as seen in historical data [3]. In detail, 94% of the COVID-19 cases reported in our study were mild-to-moderate with symptoms that are common with COVID-19, such as fever, cough, sore throat, body aches, and fatigue. These mild-to-moderate cases were treated with various therapies including antiviral medications, anti-inflammatory medications, or no medications. There were two severe cases requiring hospitalization, both of which involved risk factors (diabetes, IST, BZD) shown by previous studies for severe COVID-19 outcomes. To illustrate, a study of the COVID-19 outcomes in individuals with MS demonstrated that MS patients on B-cell-depleting therapies are at a higher risk for hospitalization and need for mechanical ventilation [7]. This has also been seen with other conditions like rheumatoid arthritis [8]. Similarly, chronic use of BZD has been shown to be associated with severe COVID-19 outcomes [9]. Although the presence of COVID-19 risk factors in our severe cases supports previous studies by demonstrating comorbidities and receiving IST or BZD as COVID-19 risk factors, the small sample size and lack of a control group limit full interpretability as it relates to SPSD as a separate risk as well as determining to what degree each of these risk factors contributes to individuals developing severe COVID-19 in SPSD.

Another COVID-19 risk factor existing among our study participants was mobility impairment. Several studies on COVID-19 risk factors in MS have shown that the degree of ambulatory impairment is highly associated with COVID-19 severity in people with MS [4, 5]. Only one person reported to be wheelchair-bound whose COVID-19 case was mild-to-moderate (mRS = 3). One of our severe cases involved a patient with mobility impairment using a unilateral ambulatory assistive device; no recent pre-COVID mRS was available for this case. There were four other participants using the same type of assistive device as this participant, all of whom experienced mild-to-moderate COVID-19. Even though all of our participants with ambulatory dysfunction, except for one of them, experienced mild-to-moderate COVID-19, the small sample size and lack of a control group do not allow us to contradict the findings of previous studies regarding ambulatory dysfunction being a risk factor for adverse COVID-19 outcomes.

It is also worth noting that six of the mild-to-moderate cases were treated with Paxlovid, which is a prescription medicine used in adults to reduce the risk of developing COVID-19 complications [14]. Paxlovid seemed to be well-tolerated and might have prevented more severe illness in those treated. Besides Paxlovid, vaccination may also have contributed to the low number of severe cases in our study as 77% of our cases were post-full-vaccination cases, although not knowing the exact vaccination timing with respect to the infection onset prevents us from determining whether vaccine-induced immunity has been involved in preventing poor COVID-19 outcomes in our post-full-vaccination cases.

Our study findings are consistent with the findings of previous studies regarding the vulnerability of the COVID-19 vaccines against the Omicron variant. That is, research has shown that the Omicron variant is more likely to pass the vaccine protection and infect vaccinated individuals compared to the older variants [10, 11]. Similarly, in our study, 23 out of the 24 post-full-vaccination cases confirmed with testing, including one of the severe cases, were post-Omicron cases. Although this finding further supports the idea that the Omicron variant might be a variant of concern when it comes to COVID-19 vaccine effectiveness, due to the small sample size used in our study and the exact timing of vaccination with respect to the infection date being unknown, we are limited in our interpretability of the Omicron variant as a variant of concern in terms of COVID-19 severity and its ability to break through the vaccine-induced immunity.

In conclusion, our study showed that COVID-19 risk factors existing in SPSD population are similar to those present in the general population. Risk factors of immunosuppressant therapies, benzodiazepines, and comorbidities like diabetes, existed in both our severe cases as well as the mild-to-moderate ones. Considering this and our study limitations, namely the small size and lack of a control group, we are unable to fully interpret how much each of these risk factors has contributed to the overall COVID-19 experience of our patients.

Symptoms experienced by the SPSD patients in our study were symptoms characteristics of COVID-19 (e.g., fever, body aches, fatigue, etc.) except for neurological symptoms, which manifested as amplified SPSD symptoms or other neurological symptoms, such as cognitive dysfunction. Nonetheless, increased SPSD symptoms in the setting of COVID-19 were transient and did not worsen SPSD as highlighted by the stable mRS post-COVID-19. Overall, the fact that 77% of our cases involved patients who were fully vaccinated and that 94% of the cases in our study were mild-to-moderate despite the high prevalence of COVID-19 risk factors among our study participants adds to the importance of considering preventative measures, such as vaccination, in patients with risk factors for severe COVID-19.