Comparison of hospitalized COVID-19 and influenza patients requiring supplemental oxygen in a cohort study: clinical impact and resource consumption

BACKGROUND: To compare clinical characteristics, outcomes, and resource consumption of patients with COVID-19 and seasonal influenza requiring supplemental oxygen.

METHODS: Retrospective cohort study conducted at a tertiary-care hospital.

Patients admitted due to seasonal influenza between 2017 and 2019, or with COVID-19 between March and May 2020 requiring supplemental oxygen were compared.

Primary outcome: 30-day mortality.

Secondary outcomes: 90-day mortality and hospitalization costs.

Attempted sample size to detect an 11% difference in mortality was 187 patients per group.

RESULTS: COVID-19 cases were younger (median years, 67 (IQR 54-78) vs 76 (IQR 64-83); p < 0.001) and more frequently overweight whereas influenza cases had more hypertension, immunosuppression, and chronic heart, respiratory and renal disease.

Compared to influenza, COVID-19 cases had more pneumonia (98% vs 60%, <0.001), higher MEWS and CURB-65 scores and were more likely to show worse progression on the WHO ordinal scale (33% vs 4%; p < 0.001).

The 30-day mortality rate was higher for COVID-19 than for influenza: 15% vs 5% (p = 0.001).

The median age of non-surviving cases was 81 (IQR 74-88) and 77.5 (IQR 65-84) (p = 0.385), respectively.

COVID-19 was independently associated with 30-day (HR 4.6, 95%CI, 2-10.4) and 90-day (HR 5.2, 95%CI, 2.4-11.4) mortality.

Sensitivity and subgroup analyses, including a subgroup considering only patients with pneumonia, did not show different trends.

Regarding resource consumption, COVID-19 patients had longer hospital stays and higher critical care, pharmacy, and complementary test costs.

CONCLUSIONS: Although influenza patients were older and had more comorbidities, COVID-19 cases requiring supplemental oxygen on admission had worse clinical and economic outcomes.