In response to restrictions on electroconvulsive therapy (ECT) access during COVID-19, we designed a trial to assess the clinical outcomes service impacts, employing an extended course of accelerated intermittent theta burst stimulation (aiTBS), in patients with moderate to severe depression in need of ECT. This open label clinical trial was comprised of 3 phases: (i) an acute phase, where iTBS treatments were administered 8 times daily, for up to 10 days; (ii) a tapering phase of 2 treatment days per week for 2 weeks, followed by 1 treatment day per week for 2 weeks; and (iii) a symptom-based relapse prevention phase, whereby treatments were scheduled based on symptom re-emergence, for up to 6 months. Of the 155 patients who completed the acute phase of the study, the remission rate was 16.1%. The mean reduction from baseline on the HRSD-24 was 29.4% (p < 0.001) and the response rate was 25.2%. Of the 110 patients who completed the tapering phase, the mean reduction from baseline was 42.6% (p < 0.001) and response and remission rates were 49.6% and 34.8%, respectively. Of the 61 patients who were eligible for the relapse prevention phase, 43 completed, with a mean reduction from baseline of 60.1% (p < 0.001); 7 patients relapsed during this phase. This study demonstrated that an extended aiTBS protocol safely led to meaningful clinical outcomes in patients with severe depression, who otherwise would have received ECT, and thus reduced pressure on ECT services during the pandemic. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT04384965 ( https://clinicaltrials.gov/study/NCT04384965?term=NCT04384965&rank=1 ).