All-Cause and Cause-Specific Mortality Attributable to Seasonal Influenza: A Nationwide Matched Cohort Study

Abstract

Background Although influenza poses substantial mortality burden, most studies have estimated excess mortality using time-aggregated data. Here, we estimated mortality risk and population attributable fraction (PAF) attributed to seasonal influenza using individual-level data from a nationwide matched cohort. Methods Individuals with influenza during four consecutive influenza seasons (2013–2017) (n = 5,497,812) and 1:4 age- and sex-matched individuals without influenza (n = 20,990,683) were identified from a national health insurance database. The endpoint was mortality within 30 days after influenza diagnosis. All-cause and cause-specific mortality risk ratios (RRs) attributed to influenza were estimated. Excess mortality, mortality RR, and PAF of mortality were determined, including for underlying disease subgroups. Results Excess mortality rate, mortality RR, and PAF of all-cause mortality were 49.5 per 100,000, 4.03 (95% confidence interval [CI], 3.63–4.48), and 5.6% (95% CI, 4.5–6.7%). Cause-specific mortality RR (12.85; 95% CI, 9.40–17.55) and PAF (20.7%; 95% CI, 13.2–27.0%) were highest for respiratory diseases. In subgroup analysis according to underlying disorders, PAF of all-cause mortality was 5.9% (95% CI, 0.6–10.7%) for liver disease, 5.8% (95% CI, 2.9–8.5%) for respiratory disease, and 3.8% (95% CI, 1.4–6.1%) for cancer. Conclusion Individuals with influenza had a 4-fold higher mortality risk than individuals without influenza. Preventing seasonal influenza may lead to 5.6% and 20.7% reductions in all-cause and respiratory mortality, respectively. Individuals with respiratory disease, liver disease, and cancer may benefit from prioritization when establishing influenza prevention strategies.

Changes in Epidemiology and Antibiotic Prescription of Influenza: Before and after the Emergence of COVID-19

“…Chronic kidney disease, congestive heart failure, ischemic heart disease, diabetes mellitus, obesity, and cancer were frequent comorbidities in patients with fatal outcomes [ 27 ]. It is well stated in the literature that older patients with comorbidities are at the highest risk of death from influenza [ 28 ]. One notable exception beyond the CCI was an early post-natal patient who developed severe influenza and died, once again underlining the importance of vaccination in this population.…”

Amelioration of the Influenza Epidemic Alert

“…Seasonal influenza demands public health attention in both hemispheres due to its severity and pandemic potential. 1 2 Despite the unpredictability of the pandemic, we learn from the past experiences how to enhance protection for high risk populations, whom to vaccinate and how to treat. 3 4 Interpandemic Influenza planning consists of vaccination strategy, social distancing policy, diagnostic testing indications, treatment guidelines, including reimbursement and the stockpiling of antiviral drugs.…”