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Hospitalizations from COVID-19 during the most recent flu season remained significantly more deadly than those resulting from influenza, but the gap appears to have narrowed substantially since earlier in the pandemic, according to findings from Veterans Affairs' (VA) databases.

Examining over 11,000 hospitalizations due to either of the two infections during this past fall and winter, 5.97% of the COVID-19 patients died within 30 days of admission versus 3.75% of the flu patients, reported Ziyad Al-Aly, MD, of VA St. Louis Health Care System in Missouri, and colleagues.

In a propensity score-matched analysis accounting for age, sex, prior infection, and a host of other factors, this difference translated to a 61% higher risk for death in the group with COVID (HR 1.61, 95% CI 1.29-2.02), the authors detailed in a research letter published in .

Furthermore, COVID-19 made up the bulk of the hospitalizations during the study period (8,996 vs 2,403 from the flu), resulting in over seven times more patient deaths (538 vs 76).

"However, the difference in mortality rates between COVID-19 and influenza appears to have decreased since early in the pandemic," said Al-Aly and co-authors.

In 2020, mortality rates for hospitalized COVID patients ranged from to depending on the study, roughly three times greater than the 6% rate in the current study, the authors noted. For flu hospitalizations, death rates were virtually the same (3.8% in 2020).

"The decline in death rates among people hospitalized for COVID-19 may be due to changes in SARS-CoV-2 variants, increased immunity levels (from vaccination and prior infection), and improved clinical care," the group suggested.

Except for individuals 65 and younger, where death rates at 30 days were nearly identical between COVID and flu patients (1.29% vs 1.33%), all other groups had a higher rate of death after COVID.

Increased risk of death versus the flu was greatest among individuals unvaccinated against COVID (8.75% vs 3.86%; HR 2.32, 95% CI 1.80-3.00), and risk significantly decreased with the number of COVID-19 vaccinations, "findings that highlight the importance of vaccination in reducing risk of COVID-19 death," wrote Al-Aly and colleagues.

People with COVID were also at higher risk of death versus the flu if they were over 65 or received no outpatient treatment -- e.g., nirmatrelvir-ritonavir (Paxlovid), molnupiravir (Lagevrio), or remdesivir (Veklury).

For their study, Al-Aly's team used electronic health databases from the VA, enrolling all individuals hospitalized from October 2022 to January 2023 with an admission diagnosis for COVID-19 or influenza, along with a positive test 2 days before or up to 10 days after admission. Individuals with dual infections were excluded.

After propensity weighting, patients had an average age of 73 years, 71% were white, 23% were Black, and 95% were men. Average body mass index was 28, and mean estimated glomerular filtration rate was 64-65. About one in five had previously had COVID, and about 63% were current or former smokers.

For vaccination history, a little less than two-thirds had received the flu vaccine and three-fourths received at least two doses of COVID vaccine, with 55% having received a booster as well.

Only 2% of the hospitalized COVID-19 cases had received antivirals in the outpatient setting, while 24% received remdesivir during inpatient care. In the cases of influenza, oseltamivir was administered to 6% in the outpatient setting and to 82% during hospitalization.

Limitations cited by the study authors included the common one seen with most VA studies (an older, predominantly male population), along with the fact that the results may not reflect the risk differences for non-hospitalized cases. Also, causes of death were not analyzed and residual confounding may have occurred.

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