SARS-CoV-2 infection among patients with autoimmune rheumatic diseases; comparison between the Delta and Omicron waves in Israel

Objective: The Omicron variant of the coronavirus SARS-CoV-2 (COVID-19) had milder clinical impacts than prior variants. This study aimed to describe the impact of COVID-19 on Autoimmune Rheumatic Disease (ARD) patients during the Delta and Omicron variants waves. Methods: We used data from Clalit Health Services (CHS), the largest health service in Israel. ARD patients diagnosed with COVID-19 between July 1, 2021, to December 1, 2021, were included in the Delta group. Patients diagnosed between December 2, 2021, to March 31, 2022, were included in the Omicron group based on the predominance of COVID-19 in Israel. The study outcomes were COVID-19-related hospitalization or death. Results: The final study cohort included 8443 actively treated ARD patients diagnosed with COVID-19. 1204 patients were positive during the predefined Delta variant period, and 7249 were positive during the predefined Omicron variant period). Compared to the Delta group, the Omicron group showed a lower rate of COVID-19-related hospitalization (3.9% vs. 1.3% for the Delta Vs. Omicron accordingly, p<0.001) and COVID-19-related death (3.2% vs. 1.1% for the Delta Vs. Omicron accordingly, p<0.001). After applying multivariable regression models, the Omicron group showed a lower risk for COVID-19-related hospitalization (Relative risk 0.4, 95% CI 0.27–0.59) and COVID-19-related mortality (RR 0.48, 95% CI 0.31–0.75). Conclusion: ARD patients infected with the COVID-19 Omicron variant had a lower risk of developing COVID-19-related adverse outcomes compared to the Delta variant.