Increased rate of hospitalisation for COVID-19 among rituximab-treated multiple sclerosis patients: A study of the Swedish multiple sclerosis registry.

Background: The primary objective of this study was to analyse the association between multiple sclerosis (MS) disease-modifying therapy (DMT) exposure and hospitalisation in patients infected with COVID-19.

Methods: Associations between MS DMT exposure and COVID-19 hospitalisation were analysed using univariable and multi-variable-clustered propensity score weighted logistic regression, where the models were clustered on the individual patients to control for patients contributing multiple COVID-19 episodes.

Findings: As of 18 January 2021, a total of 476 reported COVID-19 cases had been recorded in MS patients in the Swedish MS registry. Of these, 292 (61.3%) had confirmed COVID-19. The mean value (standard deviation (SD)) age at infection was 44.0 years (11.6). Of the 292 confirmed infections, 68 (23.2%) required hospitalisation. A total of 49 of the 164 confirmed COVID-19 patients on rituximab at baseline (29.9%) required hospitalisation, compared to a rate of 12.7% for all other DMTs combined. Rituximab in confirmed COVID-19 patients was associated with 2.95 times the odds of hospitalisation relative to any other DMT combined (odds ratio = 2.95; 95% confidence interval (CI) = 1.48-5.87).

Interpretation: Rituximab treatment, known to increase the risk of severe infections in general, also confers such a risk for MS patients with COVID-19, in comparison with other MS DMTs.