Background The COVID-19 pandemic challenges neurologists in counselling patients with multiple sclerosis (pwMS) regarding their risk by SARS-CoV-2 and in guiding disease-modifying treatment (DMT). Objective To characterize the prevalence and outcome of COVID-19 in pwMS specifically associated with different DMT in a nationwide population-based study. Methods We included patients aged ≥18 years with a confirmed diagnosis of MS and a diagnosis of COVID-19 established between January 1, 2020 and December 31, 2020. We classified COVID-19 course as either mild, severe or fatal. Impact of DMT and specifically immunosuppressants (alemtuzumab, cladribine, fingolimod, ocrelizumab or rituximab) on COVID-19 outcome was determined by multivariable models, adjusted for a-priori-risk. Results Of 126 MS patients with COVID-19 (mean age 43.2 years [SD 13.4], 71% female), 86.5% had a mild course, 9.5% a severe course and 3.2% died from COVID-19. A-priori-risk significantly predicted COVID-19 severity (R2 0.814; p<0.001) and mortality (R2 0.664; p<0.001). Adjusting for this a-priori-risk, neither exposure to any DMT nor exposure to specific immunosuppressive DMT were significantly associated with COVID-19 severity (odds ratio [OR] 1.6; p = 0.667 and OR 1.9; p = 0.426) or mortality (OR 0.5; p = 0.711 and 2.1; 0.233) when compared to no DMT. Conclusions In a population-based MS cohort, COVID-19 outcome was not associated with exposure to DMT and immunosuppressive DMT when accounting for other already known risk factors. This provides reassuring evidence that COVID-19 risk can be individually anticipated in MS and–except for a very small proportion of high-risk patients–treatment decisions should be primarily focused on treating MS rather than the pandemic.

Background: Knowledge on immunity after SARS-CoV-2 infection in patients with multiple sclerosis (pwMS) and the impact of disease-modifying treatment (DMT) is limited. Objective: To evaluate degree, duration and potential predictors of specific humoral immune response in pwMS with prior COVID-19. Methods: Anti-SARS-CoV-2 antibody testing was performed in pwMS with PCR-confirmed diagnosis of symptomatic COVID-19 from a nation-wide registry. Predictors of seropositivity were identified by multivariate regression models. Results: In 125 pwMS (mean age = 42.4 years (SD = 12.3 years), 70% female), anti-SARS-CoV-2 antibodies were detected in 76.0% after a median of 5.2 months from positive PCR. Seropositivity rate was significantly lower in patients on IS-DMT (61.4%, p = 0.001) than without DMT or immunomodulatory DMT (80.6%; 86.0%, respectively). In multivariate analysis, IS-DMT was associated with reduced probability of seropositivity (odds ratio (OR): 0.51; 95% confidence interval (95% CI): 0.17–0.82; p < 0.001). Predefined subgroup analyses showed marked reduction of seropositivity in pwMS on rituximab/ocrelizumab (OR 0.15; 95% CI: 0.05–0.56; p < 0.001). Rate of seropositivity did not change significantly over 6 months. Conclusions: Humoral immunity is stable after SARS-CoV-2 infection in MS, but is reduced by immunosuppressive DMT, particularly anti-CD20 monoclonal antibodies. This provides important evidence for advising pwMS as well as for planning and prioritizing vaccination.

Background and purpose COVID‐19 continues to challenge neurologists in counseling persons with multiple sclerosis (pwMS) regarding disease‐modifying treatment (DMT) and vaccination. The objective here was to characterize predictors of COVID‐19 outcome in pwMS. Methods We included pwMS with polymerase chain reaction‐confirmed COVID‐19 diagnosis from a nationwide population‐based registry. COVID‐19 outcome was classified as either mild or severe. Impact of DMT, specifically anti‐CD20 monoclonal antibodies (anti‐CD20), and vaccination on COVID‐19 outcome was determined by multivariate models adjusted for a priori risk (determined by a cumulative risk score comprising age, disability, and comorbidities). Results Of 317 pwMS with COVID‐19 (mean age = 41.8 years [SD = 12.4], 72.9% female, median Expanded Disability Status Scale = 1.5 [range = 0–8.5], 77% on DMT [16% on anti‐CD20]), 92.7% had a mild course and 7.3% a severe course, with 2.2% dying from COVID‐19. Ninety‐seven pwMS (30.6%) were fully vaccinated. After a median 5 months from vaccination to SARS‐CoV‐2 infection (range = 1–9), severe COVID‐19 occurred in 2.1% of fully vaccinated pwMS compared to 9.5% in unvaccinated pwMS ( p = 0.018). A priori risk robustly predicted COVID‐19 severity ( R 2 = 0.605, p < 0.001). Adjusting for a priori risk, anti‐CD20 treatment was associated with increased COVID‐19 severity (odds ratio [OR] = 3.3, R 2 = 0.113, p = 0.003), but exposure to any other DMT was not. Fully vaccinated pwMS showed a significantly decreased risk for severe COVID‐19 (OR = 0.21, R 2 = 0.144, p < 0.001). Conclusions In a population‐based MS cohort, COVID‐19 course is primarily predicted by a priori risk (depending on age, disability, and comorbidities) explaining about 60% of variance. Anti‐CD20 treatment is associated with a moderately increased risk, whereas reassuringly vaccination provides protection from severe COVID‐19.

Background and purpose Long‐term outcome after COVID‐19 in patients with multiple sclerosis (pwMS) has scarcely been studied, and controlled data are lacking. The objective of this study was to compare long‐term outcome after COVID‐19 in pwMS to a matched control group of pwMS without COVID‐19. Methods We included pwMS with polymerase chain reaction‐confirmed diagnosis of COVID‐19 and ≥6 months of follow‐up and, as a control group, pwMS matched 1:1 for age, sex, disability level, and disease‐modifying treatment type. Results Of 211 pwMS with COVID‐19 (mean age = 42.6 years [SD = 12.2], 69% female, median Expanded Disability Status Scale = 1.5 [range = 0–7.5], 16% anti‐CD20), 90.5% initially had a mild COVID‐19 course. At follow‐up, 70% had recovered completely 3 months (M3) after COVID‐19, 83% after 6 months (M6), and 94% after 12 months (M12). Mild initial COVID‐19 course was the only significant predictor of complete recovery (odds ratio [OR] = 10.5, p < 0.001). The most frequent residual symptoms were fatigue (M3: 18.5%, M6: 13.7%, M12: 7.3%), hyposmia (M3: 13.7%, M6: 5.2%, M12: 1.7%), and dyspnea (M3: 7.1%, M6: 6.6%, M12: 2.8%). Compared to matched controls, fatigue, hyposmia, and dyspnea were significantly more frequent at M3 and still slightly more frequent at M6, whereas there was no difference at M12. pwMS with COVID‐19 had neither a significantly increased risk for relapses (OR = 1.1, p = 0.70) nor disability worsening (OR = 0.96, p = 0.60). Conclusions Long‐term outcome of COVID‐19 is favorable in a large majority of pwMS, with only a small proportion of patients suffering from persistent symptoms usually resolving after 3–6 months. COVID‐19 is not associated with increased risk of relapse or disability.