Influence of Disease Modifying Treatment, Severe Acute Respiratory Syndrome Coronavirus 2 Variants and Vaccination on Coronavirus Disease 2019 Risk and Outcome in Multiple Sclerosis and Neuromyelitis Optica

Patients suffering from neuro-inflammatory diseases such as multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD) remain vulnerable to COVID-19. We investigated the risk of COVID-19 in MS and NMOSD patients over time, considering the impact of disease-modifying treatments (DMTs), vaccinations, and the spread of new SARS-CoV-2 variants. We retrospectively collected clinical information regarding all MS and NMOSD consecutive patients seen at the Neurocenter of Southern Switzerland. Logistic regression was used to test variables (age, sex, vaccination status, DMT at vaccination, DMT at infection, disease course, disability scores, prevalent SARS-CoV-2 variant) for association with COVID-19 risk and severe outcome (hospitalization or death). We included 352 individuals in this study; 315 (89.5%) received ≥1 dose of SARS-CoV-2 mRNA-vaccine, and 134 (38.1%) experienced COVID-19 between March 2020 and August 2022. COVID-19 risk decreased in vaccinated patients (OR = 0.10, 95% CI = 0.05–0.20, p < 0.001) and increased in anti-CD20 therapies (OR = 2.26, 95% CI = 1.28–4.00, p = 0.005). Anti-CD20 treatment was associated with severe COVID-19 (OR = 27.41, 95% CI = 3.68–204.25, p = 0.001), whereas Omicron infections were milder compared to Alpha infections (OR = 0.03, 95% CI = 0.01–0.35, p = 0.006). We confirmed a protective effect of mRNA vaccines on COVID-19 risk, which is impaired by anti-CD20 treatment. We provided evidence for milder COVID-19 with the Omicron SARS-CoV-2 variant, which should not, however, discourage vaccinations.