Introduction: The SARS-CoV-2 pandemic necessitated better understanding of the impact of disease-modifying therapies on COVID-19 outcomes and vaccination. We report characteristics of COVID-19 cases and vaccination status in ofatumumab-treated relapsing multiple sclerosis (RMS) patients. ----- Methods: COVID-19 data analyzed were from the ongoing, open-label, long-term extension phase 3b ALITHIOS study from December 2019 (pandemic start) and post-marketing cases from August 2020 (ofatumumab first approval) up to 25 September 2021. COVID-19 cases, severity, seriousness, outcomes, vaccination status, and breakthrough infection were evaluated. ------ Results: As of 25 September 2021, 245 of 1703 patients (14.4%) enrolled in ALITHIOS receiving ofatumumab (median exposure: 2.45 years) reported COVID-19 (confirmed: 210; suspected: 35). Most COVID-19 was of mild (44.1%) or moderate (46.5%) severity, but 9% had severe/life-threatening COVID-19. There were 24 serious cases (9.8%) with 23 patients hospitalized; 22 recovered and 2 died. At study cut-off, 241 patients (98.4%) had recovered or were recovering or had recovered with sequelae and 2 (0.8%) had not recovered. Ofatumumab was temporarily interrupted in 39 (15.9%) patients. Before COVID-19 onset, IgG levels were within the normal range in all COVID-19-affected patients, while IgM was < 0.4 g/l in 23 (9.4%) patients. No patient had a reinfection. Overall, 559 patients were vaccinated (full, 476; partial, 74; unspecified, 9). Breakthrough infection was reported in 1.5% (7/476) patients, and 11 reported COVID-19 after partial vaccination. As of 25 September 2021, the Novartis Safety Database (~ 4713 patient-treatment years) recorded 90 confirmed COVID-19 cases receiving ofatumumab. Most cases were non-serious (n = 80), and ten were serious (1 medically significant, 9 hospitalized, 0 deaths). Among 36 of 90 cases with outcomes reported, 30 recovered and 6 did not recover. ----- Conclusion: COVID-19 in RMS patients on ofatumumab was primarily of mild/moderate severity and non-serious in these observational data. Most recovered from COVID-19 without treatment interruption. Two people died with COVID-19. Breakthrough COVID-19 despite being fully/partially vaccinated was uncommon.