COVID-19 infections and vaccinations in the Swiss Multiple Sclerosis Cohort study

Background: COVID-19 disease course in MS has been described in various cohorts. Limited data is available on humoral immune responses following SARS-CoV-2 infection and vaccination. Objectives: To determine the rate of confirmed SARS-CoV-2 infection and severity of COVID-19 in a cohort of MS patients and to quantify SARS-CoV-2-specific antibody response. Methods: The study is nested within the Swiss MS Cohort, a nationwide multicenter study that has recruited 1504 persons with MS (pwMS) since 2012. PCR-confirmed SARS-CoV-2 infections, severity of COVID-19 according to the WHO clinical progression scale and immunizations with SARS-CoV-2 vaccines were captured by questionnaires used for interviews every 6 or 12 months. Anti-SARS-CoV-2 spike protein and nucleocapsid antibody levels will be determined by electrochemiluminescence immunoassay (ECLIA) (Elecsys, Anti-SARS-CoV-2, Roche Diagnostics) in sera of all participants. Results: Between February 2021 and April 2021, study questionnaires were completed for 253 pwMS (median age 47 years, 162 female). 211 pwMS (83%) had a relapsing, 25 (10%) a secondary progressive, 13 (5%) a primary progressive disease course and 4 (2%) a clinically isolated syndrome. Median disease duration was 12 years and median EDSS was 2.5. 218 (86%) pwMS were treated with DMTs: Ocrelizumab (27%), fingolimod (26%), dimethyl fumarate (15%), rituximab (10%), natalizumab (9%), other DMTs (13%). 15 (5.9%) of 253 pwMS had a positive SARSCoV- 2 PCR test since March 2020. In these pwMS, COVID-19 severity ranged from 1-10 on the WHO clinical progression scale: 1 pwMS was asymptomatic, 10 pwMS were symptomatic as outpatients (8 independently, 2 needed assistance), 3 pwMS were hospitalized (1 without oxygen therapy, 2 with oxygen by mask or nasal prongs) and 1 pwMS died. By April 2021, 24 and 38 pwMS received one and two doses of SARS-CoV-2 mRNA vaccines, respectively. Conclusions and outlook: Since start of the pandemic, rate of PCR-confirmed SARS-CoV-2 infection in our sample was slightly lower compared to incidence of laboratory-confirmed cases in Switzerland. The majority of pwMS had mild COVID-19. The study will continue until 2024 and by ECTRIMS 2021, we anticipate a doubling of completed questionnaires and to report preliminary results of serological measurements. This will allow us to present vaccine- and natural infection induced serological anti-SARS-CoV-2 responses in pwMS and assess differences related to various DMTs or COVID-19 severity.