COVID-19 outcomes more severe than those of flu, RSV
21 Mar 2025
COVID-19 led to more severe disease outcomes than influenza or respiratory syncytial virus (RSV) during the 2022–2023 season, whereas the differences were attenuated in the subsequent season, as shown in a retrospective study.
Researchers used electronic health record data from the national US Veterans Health Administration. They looked at outpatient veterans who underwent same-day testing for SARS-CoV-2, influenza, and RSV, and received a diagnosis of a single infection between 1 August 2022 and 31 March 2023 or between 1 August 2023 and 31 March 2024.
Inverse probability weighting was performed to evaluate the primary outcomes of 30-day hospitalization, intensive care unit admission, and death, as well as the secondary outcome of long-term death extending through 180 days across the study cohorts.
A total of 68,581 patients were included in the 2022–2023 cohort, of which 6,239 had RSV (9.1 percent), 16,947 had influenza (24.7 percent), and 45,395 had COVID-19 (66.2 percent). The 2023–2024 cohort, on the other hand, included 72,939 patients, of which 9,748 had RSV (13.4 percent), 19,242 had influenza (26.4 percent), and 43,949 had COVID-19 (60.3 percent). The median age of the entire population was 66 years, and 87.0 percent were male.
The 30-day risk of hospitalization during the 2023–2024 season for COVID-19 was similar with that for influenza but lower for RSV (16.2 percent vs 16.3 percent and 14.3 percent, respectively; risk difference [RD], 1.9 percent, 95 percent confidence interval [CI], 0.9–2.9; and RD, 2.0 percent, 95 percent CI, 0.8–3.3).
During the 2022–2023 season, the 30-day risk of death for COVID-19 was slightly higher than for influenza or RSV (1.0 percent vs 0.7 percent and 0.7 percent, respectively; RD, 0.4 percent, 95 percent CI, 0.1–0.6) or RSV (RD, 0.4 percent, 95 percent CI, 0.1–0.6). The risk did not differ relative to that seen during the 2023–2024 season for COVID-19.
Meanwhile, the 180-day mortality risk for COVID-19 was higher during both seasons compared with that for influenza (2023–2024: RD, 0.8 percent, 95 percent CI, 0.3–1.2) and for RSV (2023–2024: RD, 0.6 percent, 95 percent CI, 0.1–1.1).
The elevated mortality in both seasons was reported for veterans without COVID-19 vaccination in the previous year relative to veterans without seasonal influenza vaccination. Among groups vaccinated against their respective infections, mortality between COVID-19 and influenza did not differ at any time point.