Table 2.

Influenza and Respiratory Syncytial Virus (RSV)‐Attributable Cardiopulmonary Hospitalizations (Events) by Risk Group, Tennessee Medicaid Nursing Home Residents from 1995 to 1999

	Rates, Events, and Person‐Years by Season			Total Rates, Events, and Person‐ Years	Estimated Annual Events Attributable to Winter Viruses per 1,000 Person‐Years* (95% Confidence Interval)		Percentage of Total Events Attributable to Winter Viruses †
Risk Group	Influenza	RSV	Non‐winter viral		Influenza	RSV	Influenza	RSV	Both
No high risk					6.6 (4.1–9.2)	6.0 (1.9–10.0)	7.6	6.9	14.5
Hospitalizations per 1,000 person‐years	113	87	74	88
Number of hospitalizations	827	707	1,121	2,655
Person‐years	7,310	8,075	15,112	30,497
High risk					28.1 (23.4–32.9)	11.4 (3.5–19.3)	4.8	2.5	7.3
Hospitalizations per 1,000 person‐years	707	571	545	588
Number of hospitalizations	8,106	7,943	14,177	30,226
Person‐years	11,459	13,901	26,029	51,389

^* Values are weighted averages of annual excess events for a population of 1,000 persons within the specified age and risk group. The influenza excess events were calculated by multiplying the event rate difference between influenza and RSV by the proportion of overall study days in influenza season. The RSV excess events were calculated by multiplying the event rate difference between RSV and non‐winter‐viral season by the proportion of overall study days in RSV or influenza season (RSV circulated during both of these seasons). The weighted average difference in rates between influenza and RSV season and RSV season and non‐winter‐viral season were calculated with stratum‐specific person‐years in all seasons as weights; strata were defined by study year, race, sex, and nursing home location.

^† Percentage values are calculated by dividing the annual excess events attributable to influenza or RSV by the age and risk‐group specific total event rate.