While the mortality gap between COVID-19 and influenza has narrowed since the onset of the pandemic, COVID continues to carry a substantially higher short-term risk of death than seasonal flu despite the availability of a COVID vaccine, according to a large population-based cohort study from South Korea.
For the study, published last week in the International Journal of Infectious Diseases, Korean researchers drew on data from national health insurance claims to compare 30-day all-cause mortality among more than 15 million people diagnosed as having COVID or influenza from July 2022 to December 2023.
76% higher odds of death by 30 days for COVID
A COVID diagnosis was associated with 76% higher odds of death within 30 days than influenza. Overall, 0.20% of patients with COVID died, compared with 0.016% of those with influenza, a roughly 12.5-fold difference in crude mortality. Among hospitalized patients, COVID was linked to a substantially greater risk of death in those receiving mechanical ventilation (1.88-fold higher).
The mortality gap was especially pronounced among adults aged 18 to 64 years (adjusted odds ratio [OR], 2.93), hospitalized patients (aOR, 2.55), and those who had a heart attack (aOR, 2.24), chronic lung disease (aOR, 1.94), or diabetes (aOR, 1.81). Adults aged 65 and older also had increased risk, though the relative odds were lower than those of the 18- to 40-year cohort (aOR, 1.95).
One possible explanation for the age-related differences, note the authors, is Korea’s prioritization of COVID vaccines for older adults and those in high-risk groups. They also cite differences in coverage between the two vaccines and differences in vaccine uptake as contributing factors. Among adults 65 and older, uptake for influenza vaccines was 82.5% in 2023-24 but only 45% for COVID.
“This disparity may have contributed to the higher mortality observed for COVID-19,” the researchers write. “Collectively, these findings highlight the critical role of vaccination coverage in shaping mortality patterns and underscore the need for targeted strategies to improve uptake among younger populations.”
