During the 2023-24 respiratory virus season, hospitalized US COVID-19 patients were at a 35% higher risk for death from any cause than those admitted for influenza, compared with a 61% higher risk the winter before, estimates a research letter published today in JAMA.
Researchers from the Veterans Affairs St. Louis Health Care System in Missouri mined US Department of Veterans Affairs electronic health records from all 50 US states for data on patients hospitalized for COVID-19 or flu from October 2023 to March 2024. The study period included the emergence of the JN.1 SARS-CoV-2 variant in December 2023. Follow-up was 30 days or until death. Causes of death weren't examined.
Nonsignificant difference during JN.1
A total of 8,625 patients were hospitalized for COVID-19 at 30 days (unadjusted death rate, 5.70%), and 2,647 were admitted for flu (unadjusted death rate, 3.04%).
Compared with a study using the same database and methods, the death rate at 30 days was 5.97% in 2022-2023 vs 5.70% in 2023-2024 for COVID-19 and 3.75% in 2022-2023 vs 4.24% in 2023-2024 for influenza.
COVID-19 patients were more likely to die than those with flu by 30 days (adjusted death rate, 5.70% vs 4.24%; adjusted hazard ratio [HR], 1.35), but the difference between the two groups was nonsignificant immediately before and during JN.1 variant predominance (adjusted death rate, 5.46% vs 5.82%; adjusted HR, 1.07).
"Compared with a study using the same database and methods, the death rate at 30 days was 5.97% in 2022-2023 vs 5.70% in 2023-2024 for COVID-19 and 3.75% in 2022-2023 vs 4.24% in 2023-2024 for influenza," the study authors wrote. "Both adjusted HRs were statistically significant, with an HR of 1.61 in 2022-2023 and 1.35 in 2023-2024, with overlapping 95% CIs [confidence intervals]."
The team said that mutations in the COVID-19 or flu viruses and/or the use of vaccines or antiviral drugs influence the relative risk of death. They also noted that the results should be interpreted in the context of nearly twice as many hospitalizations for COVID-19 than for flu during the 2023-24 respiratory virus season.
The finding that, at the level of the study's statistical power, the risk of death wasn't significantly different in the COVID-19 and flu cohorts in the JN.1-dominant era suggests that the variant may have a similar severity profile as the variants emerged immediately before, the researchers said. Because most participants were older men, they cautioned that the results may not be generalizable to the rest of the population.
