Comparative Burden of COVID-19 in Adults with Rheumatic Diseases and Immunocompetent Individuals: A Population-Based Cohort Study in Quebec, Canada, 2020-2023

Introduction: Across major phases of the COVID-19 pandemic (March 2020-April 2023), we compared the burden of severe COVID-19 among individuals with systemic autoimmune rheumatic diseases (SARDs) versus immunocompetent individuals with and without comorbidities. Methods: This population-based cohort study used administrative datasets to estimate crude and age- and sex-standardized SARS-CoV-2 and severe COVID-19 incidences among adults >18 years with SARDs, chronic comorbidities, or no comorbidities. Relative to the latter, we used Cox models to derive adjusted hazard ratios (aHRs) for infection, hospitalization, and intensive care unit admission or death (ICU/death) during the pre-vaccination (March-December 2020), vaccination pre-Omicron (December 2020-December 2021), and Omicron (December 2021-April 2023) periods. Results: We included 81,434 adults with SARDs, and 2,020,356 with comorbidities versus 3,144,700 without comorbidities. Despite similar adjusted infection rates, the SARDS cohort had higher risks of hospitalization and ICU/death during the pre-vaccination period (aHRs: 3.4, 95%CI:2.8-4.1; and 4.0, 95%CI:2.8-5.7, respectively), persisting through the Omicron period (aHRs: 4.5, 95%CI:4.0-4.9; and 4.4, 95%CI:3.6-5.4, respectively). Among SARDS, rheumatoid arthritis, psoriatic arthritis and systemic lupus erythematosus contributed highest burden, with comparable hospitalization and mortality rates among younger rheumatoid arthritis versus healthy older adults. Highly immunosuppressive rituximab- or mycophenolate-treated patients had highest hospitalization and ICU/death risks, particularly during the Omicron period (aHRs: 11.9, 95%CI:9.9-14.3; and 17.6, 95%CI:13.0-23.9, respectively). Conclusion: Individuals with SARDs, especially receiving highly immunosuppressive therapies, experienced elevated COVID-19 burden and severe outcome risks throughout the pandemic, warranting their prioritized consideration during future public health emergencies.