Table 4.

Comparison of estimated risk of death associated with influenza season using different methods of defining the influenza season.

Flu Season Definition	Unadjusted Hazard Ratio (95% CI)	Adjusted Hazard Ratio* (95% CI)	Number of deaths attributable to influenza	Rate of Attributable Excess Deaths** (95%CI)
5% Moving Average	1.10 (0.98–1.22)	1.16 (1.04–1.29)	66	4.69 (3.61 to 5.96)
10% Moving Average	1.03 (0.92–1.15)	1.08 (0.97–1.21)	27	1.92 (1.27 to 2.79)
First/Last Isolate	1.11 (0.995–1.24)	1.19 (1.06–1.33)	114	8.10(6.59 to 9.85)
5% Total Season Isolates	0.997 (0.881–1.13)	1.04 (0.92–1.18)	10	0.71 (0.34 to 1.31)

CI = confidence interval;

* adjusted for trial, age group, NYHA class, co-morbidity index score, enalapril therapy, ejection fraction, and study site.

**Rates are per 1,000 patient-years