Impact of COVID-19 vaccination or infection on disease activity in a radiologically isolated syndrome cohort: The VaxiRIS study

Introduction: Nowadays, mandatory vaccination in patients with multiple sclerosis (MS) is widely recommended. Regarding COVID19, the absence of specific warnings led to the proposal of vaccination in patients with inflammatory diseases of the central nervous system. However global vaccination hesitancy remains and potential effect of COVID19 vaccination on disease activity needs to be assessed.Objectives: We aimed to evaluate if COVID19 vaccination or infection increased the risk of clinical conversion to multiple sclerosis or evidence of disease activity (EDA) in a cohort of RIS subjects.Methods: This multicentric observational study is based on the RISC cohort. Data regarding COVID19 infection and vaccination has been collected between January 2020 and December 2021. We compared the occurrence of clinical conversion to MS and EDA in patients according to their vaccination status. The same analysis was conducted by comparing patients according to their history of COVID19 infection.Results: 217 subjects with known vaccination status were included (Mean age: 44yrs, F/M sex ratio 2.7). 80% of subjects had a complete vaccination and 20% were incompletely or not vaccinated. Both groups did not differ regarding the main demographical data and known risk factors of conversion to MS. No difference was found concerning clinical conversion to MS in the vaccinated versus unvaccinated group (2.4% versus 2.5%, p = 0.9747). We did not observe any statistical difference regarding the rate of EDA in both groups.20% of subjects had a history of COVID-19 infection. The rate of clinical conversion to MS in the infected compared to the non-infected group did not show any differenceThe global conversion rate to MS in the whole RISC cohort in 2021 was 2.64%, which is comparable with the observed rates during the four previous years (5.75%, 2.55%, 4.79%, and 4.85% per year respectively).Conclusions: Our study suggests that COVID19 vaccination does not increase the risk of clinical conversion to MS in RIS subjects and supports that immunization can be safely proposed for these patients.