A nationwide multistate analysis estimating the rates and risks of transferring critically ill COVID-19 patients during the Delta and Omicron waves in Germany

BackgroundThe spread of several SARS-CoV-2 variants of concern (VOC) led to increasing numbers of patients with coronavirus disease 2019 (COVID-19) in German intensive care units (ICU), resulting in capacity shortages and even transfers of COVID-19 ICU patients between federal states in late 2021. Comprehensive evidence on the impact of predominant VOC, in this case Delta and Omicron, on inter-hospital transfers of COVID-19 ICU patients remains scarce. MethodsA retrospective cohort study was conducted from July 01, 2021 until May 31, 2022 using nationwide reimbursement inpatient count data of COVID-19 ICU patients and weekly sequence data of VOC in Germany. A multivariable Poisson regression analysis was performed to estimate incidence rates and incidence rate ratios (IRR) for competing events of transfer, discharge and death, adjusted for VOC infection, age group and sex. For corresponding risk estimation, a multistate model for the clinical trajectory in ICU was applied. ResultsOmicron versus Delta infection yielded estimated adjusted IRR of 1.23 (95% CI, 1.16 - 1.30) for transfer, 2.27 (95% CI, 2.20 - 2.34), for discharge and 0.98 (95% CI, 0.94 - 1.02) for death. For death in ICU, estimated adjusted IRR increased progressively with age up to 4.09 (95% CI, 3.74 - 4.47) for those 90 years and older. COVID-19 ICU patients with Omicron infection were at comparatively higher estimated risk of discharge, whereas the estimated risk of transfer and death were higher for those with Delta infection. ConclusionsInter-hospital transfers and discharges occurred more frequently in COVID-19 ICU patients with Omicron infection than in those with Delta infection, who in turn had a higher estimated risk of death. Age emerges as a relevant determinant for fatal clinical trajectories in COVID-19 ICU patients and imposes close therapeutic care.