Table 2. Oseltamivir prescription rates/100,000 enrollees by age and chronic disease classification, United States, weeks 36–44, 2004 and 2005.

Characteristic	2004	2005	Rate ratio (2005/2004)	95% Confidence interval
Age group, y
<1	0.26	10.65	40.7	(5.6–294)
1–4	8.95	65.95	7.4	(6.3–8.6)
5–17	11.12	81.28	7.3	(6.8–7.9)
18–24	19.55	81.42	4.2	(3.8–4.5)
25–49	33.08	120.97	3.7	(3.5–3.8)
50–64	63.33	211.26	3.3	(3.2–3.4)
>65	69.04	168.20	2.4	(2.4–2.5)
Chronic disease classification*
Pulmonary	77.66	268.50	3.46	(3.33–3.60)
Immune deficient	67.75	240.16	3.54	(3.21–3.91)
Neurologic	54.57	207.43	3.80	(3.47–4.15)
Cardiac	54.11	196.92	3.64	(3.54–3.74)
Diabetes	50.85	143.85	2.83	(2.64–3.02)
Chronic disease absent	14.07	89.50	6.36	(6.10–6.62)
*Rates from chronic disease classification include only enrollees >18 y of age. Except for the chronic disease absent category, all chronic disease classifications were not mutually exclusive. Chronic disease classification is derived from the chronic disease index, which has been validated (10).