Background: Disease-modifying therapies (DMTs) used to treat multiple sclerosis (MS) alter the immune system and therefore increase the risk of infection. There is growing concern about the impact of COVID-19 on patients with MS (pwMS), especially those treated with DMTs. Methods: This is a single-center prospective observational study based on data from the Esclerosis Múltiple y COVID-19 (EMCOVID-19) study. Demographic characteristics, MS history, laboratory data and SARS-CoV-2 serology, and symptoms of COVID-19 in pwMS treated with any DTM were extracted. The relationship among demographics, MS status, DMT, and COVID-19 was evaluated. Results: A total of 259 pwMS were included. The administration of interferon was significantly associated with the presence of SARS-CoV-2 antibodies (26.4% vs. 10.7%, p = 0.006). Although patients taking interferon were significantly older (49.1 vs. 43.5, p = 0.003), the association of interferon with the presence of SARS-CoV-2 antibodies was still significant in the multivariate analysis (OR 2.99 (1.38; 6.36), p = 0.006). Conclusions: According to our data, pwMS present a higher risk of COVID-19 infection compared with results obtained from the general population. There is no evidence of a worse COVID-19 outcome in pwMS. DMTs did not significantly change the frequency of COVID-19, except for interferon; however, these findings must be interpreted with caution given the small sample of pwMS taking each DMT.
Keywords: COVID-19; DMT; SARS-CoV-2; multiple sclerosis; seroprevalence.