Tixagevimab/Cilgavimab does not prevent COVID-19 in patients with multiple sclerosis and related disorders on B-cell depleting therapies

Background: Patients with MS and related disorders (pwMSARD) on B -cell depleting treatments have attenuated immune responses to vaccination and were eligible to receive tixagevimab/cilgavimab. Objectives: Understand incidence and severity of COVID-19 in pwMSARD on B -cell depleting therapies who received tixagevimab/cilgavimab compared to an untreated group. Methods: We conducted a retrospective medical records review of adult pwMSARD on B -cell depleting treatments who received tixagevimab/cilgavimab between 1/2022 -1/2023. PwMSARD on B -cell depleting treatments who did not served as a control group (CG). We compared COVID-19 incidence and severity within 6 months of tixagevimab/cilgavimab or rituximab/ocrelizumab infusion for the CG. Results: 210 patients were identified, 135 in the treatment group (TG) and 75 in the CG. In the TG, 24 (17.8 %) developed COVID-19 compared to 12 (16 %) in the CG. There was no difference in the odds of developing COVID-19 in an unadjusted logistic regression model (OR =1.14; 95 % CI: 0.53, 2.42; p = 0.74) or after adjusting for age and disease duration (OR =1.05; 95 % CI: 0.47, 2.37; p = 0.91). There was also no difference in COVID-19 severity between groups. Conclusions: There was no difference in COVID-19 infection rates or severity in pwMSARD on B -cell depleting treatments who received tixagevimab/cilgavimab compared to those who remained untreated.