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. 2024 Sep 23;24(1):1107.
doi: 10.1186/s12913-024-11493-z.

Assessing the impact of Delta and Omicron in German intensive care units: a retrospective, nationwide multistate analysis

Matthäus Lottes  1 , Marlon Grodd  2 , Linus Grabenhenrich  3 , Martin Wolkewitz  2
Affiliations

Assessing the impact of Delta and Omicron in German intensive care units: a retrospective, nationwide multistate analysis

Matthäus Lottes et al. BMC Health Serv Res. .

Abstract

Background: The spread of several severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) variants of concern (VOCs) has repeatedly led to increasing numbers of coronavirus disease 2019 (COVID-19) patients in German intensive care units (ICUs), resulting in capacity shortages and even transfers of COVID-19 intensive care patients between federal states in late 2021. In this respect, there is scarce evidence on the impact of predominant VOCs in German ICUs at the population level.

Methods: A retrospective cohort study was conducted from July 01, 2021, to May 31, 2022, using daily nationwide inpatient billing data from German hospitals on COVID-19 intensive care patients and SARS-CoV-2 sequence data from Germany. A multivariable Poisson regression analysis was performed to estimate the incidence rate ratios (IRRs) of transfer (to another hospital during inpatient care), discharge (alive) and death of COVID-19 intensive care patients associated with Delta or Omicron, adjusted for age group and sex. In addition, a multistate approach was used for the clinical trajectories of COVID-19 intensive care patients to estimate their competing risk of transfer, discharge or death associated with Delta or Omicron, specifically concerning patient age.

Results: A total of 6046 transfers, 33256 discharges, and 12114 deaths were included. Poisson regression analysis comparing Omicron versus Delta yielded an estimated adjusted IRR of 1.23 (95% CI 1.16-1.30) for transfers, 2.27 (95% CI 2.20-2.34) for discharges and 0.98 (95% CI 0.94-1.02) for deaths. For ICU deaths in particular, the estimated adjusted IRR increased from 0.14 (95% CI 0.08-0.22) for the 0-9 age group to 4.09 (95% CI 3.74-4.47) for those aged 90 and older compared to the reference group of 60-69-year-olds. Multistate analysis revealed that Omicron was associated with a higher estimated risk of discharge for COVID-19 intensive care patients across all ages, while Delta infection was associated with a higher estimated risk of transfer and death.

Conclusions: Retrospective, nationwide comparisons of transfers, discharges and deaths of COVID-19 intensive care patients during Delta- and Omicron-dominated periods in Germany suggested overall less severe clinical trajectories associated with Omicron. Age was confirmed to be an important determinant of fatal clinical outcomes in COVID-19 intensive care patients, necessitating close therapeutic care for elderly people and appropriate public health control measures.

Keywords: COVID-19; Competing risk; Intensive care unit; Multistate model; Variant of concern.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Graphical representation of a multistate model for the clinical trajectories and outcomes of COVID-19 intensive care patients in Germany based on nationwide inpatient billing data from the Institute for the Hospital Remuneration System GmbH (InEK)
Fig. 2
Fig. 2
Line plot for the estimated risk of transfer (to another hospital during inpatient care) for COVID-19 intensive care patients in Germany by predominant SARS-CoV-2 variant of concern (dashed line: Omicron, solid line: Delta) and age group up to Day 15 after initial intensive treatment
Fig. 3
Fig. 3
Line plot for the estimated risk of discharge (alive) for COVID-19 intensive care patients in Germany by predominant SARS-CoV-2 variant of concern (dashed line: Omicron, solid line: Delta) and age group up to Day 15 after initial intensive treatment
Fig. 4
Fig. 4
Line plot for the estimated risk of death for COVID-19 intensive care patients in Germany by predominant SARS-CoV-2 variant of concern (dashed line: Omicron, solid line: Delta) and age group up to Day 15 after initial intensive treatment
See this image and copyright information in PMC

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