Looking back, what have we learnt?

ABSTRACT

Introduction: Since the beginning of the COVID-19 pandemic, national and international registries of COVID-19 in patients with multiple sclerosis (MS) identified the most important risk factors for developing a severe form of COVID-19, mainly defined by oxygen-dependent pneumonia, and in the most severe cases the need for ventilation or death. Objective(s) to provide an overview of what we have learned about COVID-19 in patients with MS over the past 2 years Results: Although the majority of patients who died from COVID- 19 were patients with high neurological disability or other severe co-morbidities, anti-CD20 therapy was rapidly identified as a factor associated with worse prognosis of COVID-19, unlike other MS disease modifying therapies. A recent analysis of the COVISEP registry (2635 COVID-19 cases in patients with MS) with propensity scores found that this deleterious effect of anti-CD20 was predominant in the relapsing-remitting group only. This higher risk of severe COVID-19 associated with anti-CD20 therapy has led to prioritising patients on anti-CD20 for access to anti-COVID treatments, either pre-exposure or in case of infection. Anti-CD20 therapy has also been associated with a decreased humoral response after infection and an increased risk of postvaccination infection. With new Omicron variant subtypes and the advent of vaccination, the symptoms of COVID-19 and their severity have been largely modified, with severe forms becoming rarer. Conclusion(s) Overall, the therapeutic decision strategy for MS has been little changed in the era of COVID-19, given the major benefit of high efficacy therapies in relapsing remitting MS, but therapeutic choices in progressive patients must weigh the increased risk of severe COVID-19 in patients with higher disability against the modest therapeutic efficacy of approved or off-label treatments for progressive MS.