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Table 2 Comparison of estimated risk of hospitalization associated with influenza season using different methods of defining the influenza season.

From: Comparing estimates of influenza-associated hospitalization and death among adults with congestive heart failure based on how influenza season is defined

Flu Season Definition Unadjusted Hazard Ratio (95% CI) Adjusted Hazard Ratio* (95% CI) Number of hospitalizations attributable to influenza Rate of Attributable Excess hospitalizations** (95%CI)
5% Moving Average 1.09 (1.02–1.17) 1.10 (1.04–1.18) 109 12.72 (10.35 to 15.47)
10% Moving Average 1.04 (0.97–1.11) 1.09 (1.02–1.17) 74 8.64 (6.74 to 10.58)
First/Last Isolate 1.07 (0.995–1.14) 1.08 (1.01–1.16) 132 15.41 (12.54 to 18.74)
5% Total Season Isolates 1.07 (0.989–1.15) 1.08 (1.00–1.17) 51 5.95 (4.43 to 7.82)
  1. CI = confidence interval;
  2. * adjusted for trial, age group, NYHA class, co-morbidity index score, enalapril therapy, ejection fraction, and study site.
  3. **Rates are per 1,000 patient-years