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.

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 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.