Comparative Evaluation of Risk of Death in Mechanically Ventilated Patients With COVID-19 and Influenza: A Population-Based Cohort Study

Abstract

Background: Reports on the comparative mortality among mechanically ventilated patients with coronavirus disease 2019 (COVID-19) and influenza show conflicting findings, but studies focused largely on the early phase of the pandemic, using historical influenza comparators. We sought to examine the population-level comparative mortality among mechanically ventilated patients with COVID-19 during the latter pandemic years using contemporaneous influenza comparators.

Methods: We used a statewide dataset to identify mechanically ventilated hospitalizations aged ≥ 18 years with COVID-19 or influenza in Texas between October 2021 and March 2023. Their comparative short-term mortality (in-hospital death or discharge to hospice) was estimated using overlap propensity score weighting (primary model), entropy balance, and hierarchical logistic models.

Results: Among 22,195 mechanically ventilated hospitalizations, 19,659 (88.6%) had COVID-19 and 2,536 (11.4%) had influenza. Compared to mechanically ventilated hospitalizations with influenza, those with COVID-19 were more commonly racial or ethnic minority (49.3% vs. 48.4%) and had lower mean (standard deviation (SD)) Deyo comorbidity index (2.04 (2.03) vs. 2.53 (1.91)), but higher number of organ dysfunctions (2.60 (1.37) vs. 2.13 (1.27)), respectively. Short-term mortality among mechanically ventilated hospitalizations with COVID-19 and influenza was 49.1% vs. 20.7%. The risk of short-term mortality was attenuated but remained higher among hospitalizations with COVID-19 in the primary model (adjusted risk ratio: 1.24 (95% confidence interval (CI): 1.18 - 1.30); adjusted risk difference 8.8% (95% CI: 6.7 - 10.4)), with consistent findings in alternative models, subgroups, and sensitivity analyses.

Conclusions: Population-level short-term mortality among mechanically ventilated hospitalizations with COVID-19 has been higher than that among those with influenza during the latter years of the pandemic.

Keywords: COVID-19; Influenza; Mechanical ventilation; Mortality.

Figure 1

Subgroup analysis of comparative short-term mortality among mechanically ventilated hospitalizations with COVID-19 and influenza. Analyses were conducted using overlap propensity score weighting. Adjusted risk ratio represents the risk of short-term mortality among mechanically ventilated hospitalizations with COVID-19 compared to those with influenza. Adjusted risk difference represents the absolute difference in short-term mortality among mechanically ventilated hospitalizations with COVID-19 compared to those with influenza, expressed as percentage. Non-parametric bootstrap 95% confidence intervals (CIs) were determined using 10,000 bootstrap samples and the percentile method. The width of the CIs was not adjusted for multiplicity and should not be used to infer definite effects. COVID-19: coronavirus disease 2019.