BACKGROUND AND AIMS: As no population-based study has investigated the susceptibility and disease course of COVID-19 among patients with inflammatory bowel diseases (IBD), we aimed to investigate this topic in a population-based setting. METHODS: Two cohorts were investigated. First, a nationwide cohort of all IBD patients diagnosed with COVID-19 was prospectively followed to investigate the disease courses of both diseases. Second, within a population-based cohort of 2.6 million Danish citizens, we identified all individuals tested for SARS-CoV-2 to determine the occurrence of COVID-19 among patients with and without IBD and other immune-mediated inflammatory diseases (IMIDs). RESULTS: Between January 28, 2020 and June 2, 2020, a total of 76 IBD patients with COVID-19 were identified in the national cohort and prospectively followed for 35 days (interquartile range (IQR): 25-51). A large proportion (n=19;25%) required a COVID-19-related hospitalization for seven days (IQR: 2-8.5) which was associated with being 65 years or older (odds ratio (OR)=23.80 (95% confidence interval (CI) 6.32-89.63), p<0.01) and presence of any non-IMID comorbidity (OR=8.12 (95% CI 2.55-25.87), p<0.01), but not use of immunomodulators (p=0.52) or biologic therapies (p=0.14). In the population-based study, 8,476 of 231,601 (3.7%) residents tested positive for SARS-CoV-2; however, the occurrence was significantly lower among patients with IBD (62 of the 2,486 patients=2.5%, p<0.01) and other IMIDs (531 of 16,492 patients=3.2%, p<0.01) as compared to patients without IMIDs. CONCLUSION: Patients with IMIDs, including IBD, had a significantly lower susceptibility to COVID-19 than patients without IMIDs and neither immunosuppressive therapies nor IBD activity were associated with the disease course of COVID-19.