CORONAVIRUS (COVID-19)
IMAJ | volume 25
Journal 9, September 2023
pages: 585-589
Clinical Outcomes of Hospitalized Patients with SARS-CoV-2 Omicron Variant vs. Influenza A During Influenza Season 2021 to 2022: A Retrospective Observational Study
1 Infectious Disease Unit, Rabin Medical Center (Beilinson Campus), Petah Tikva, Israel
2 COVID-19 Inpatient Department, Rabin Medical Center (Beilinson Campus), Petah Tikva, Israel
3 Internal Medicine Department E, Rabin Medical Center (Beilinson Campus), Petah Tikva, Israel
4 Statistics Division, Clinical Research Authority, Rabin Medical Center (Beilinson Campus), Petah Tikva, Israel
5 Clinical Microbiology Laboratory, Rabin Medical Center (Beilinson Campus), Petah Tikva, Israel
6 Internal Medicine Department C, Rabin Medical Center (Beilinson Campus), Petah Tikva, Israel
7 Faculty of Medicine, Tel Aviv University, Tel-Aviv, Israel
Summary
Background:
Influenza and coronavirus disease 2019 (COVID-19) are respiratory diseases with similar modes of transmission. In December 2021, influenza re-emerged after it had been undetected since March 2020 and the Omicron variant replaced the Delta variant. Data directly comparing the two diseases are scarce.
Objectives:
To compare the outcomes of patients with both the Omicron variant and influenza during 2021–2022.
Methods:
We performed a retrospective study conducted in Beilinson hospital, Israel, from December 2021 to January 2022. We included all hospitalized patients with either laboratory-confirmed COVID-19 or influenza. The primary outcome was 30-day mortality.
Results:
We identified 167 patients diagnosed with Omicron and 221 diagnosed with Influenza A. The median age was 71 years for Omicron and 65 years for influenza. Patients with Omicron had a significantly higher Charlson Comorbidity Index score (4 vs. 3,
P < 0.001). Patients with Omicron developed more respiratory failure that needed mechanical ventilation (7% vs. 2%,
P = 0.05) and vasopressors (14% vs. 2%,
P < 0.001) than patients with influenza. In a multivariate model, 30-day mortality was lower in patients diagnosed with influenza than in patients diagnosed with Omicron (19/221 [9%] vs. 44/167 [26%], hazard ratio 0.45, 95% confidence interval 0.25–0.81).
Conclusions:
Patients diagnosed with Omicron had higher mortality than patients diagnosed with seasonal influenza. This finding could be due to differences in co-morbidities, the virus pathogenicity, and host responses to infection.