Table 2. Factors associated with intensive care unit admission and death, Catalonia, influenza seasons 2010/11–2015/16 (n = 1,727).

Characteristics	ICU/death (n = 692)		Non-ICU/death (n = 1,035)		Crude OR	95% CI	p value
	n	%	n	%
Seasonal vaccination
Yes	146	21.3	304	29.7	0.64	(0.51 to 0.80)	< 0.001
No	540	78.7	721	70.3	Ref
Age
18–64 years	386	55.8	422	40.8	Ref
≥ 65 years	306	44.2	613	59.2	0.55	(0.45 to 0.66)	< 0.001
Sex
Male	271	39.2	472	45.6	0.77	(0.63 to 0.93)	0.008
Female	421	60.8	563	54.4	Ref
Type of virus
A	602	87	883	85.3	1.15	(0.87 to 1.52)	0.325
B	90	13	152	14.7	Ref
COPD
Yes	187	27.0	255	24.6	1.13	(0.91 to 1.41)	0.27
No	505	73.0	780	75.4	Ref
Obesity
Yes	87	12.6	95	9.2	1.42	(1.04 to 1.94)	0.02
No	605	87.4	940	90.8	Ref
Diabetes mellitus
Yes	170	24.6	261	25.2	0.97	(0.77 to 1.21)	0.76
No	522	75.4	774	74.8	Ref
Chronic renal disease
Yes	100	14.5	136	13.1	1.12	(0.84 to 1.47)	0.44
No	592	85.5	899	86.9	Ref
Immunodeficiency
Yes	159	23.0	177	17.1	1.45	(1.14 to 1.84)	0.003
No	533	77.0	858	82.9	Ref
Chronic cardiovascular disease
Yes	196	28.3	312	30.1	0.92	(0.74 to 1.13)	0.42
No	496	71.7	723	69.9	Ref
Chronic liver disease
Yes	58	8.4	55	5.3	1.63	(1.11 to 2.39)	0.01
No	634	91.6	980	94.7	Ref
Pregnancy
Yes	16	2.3	10	1.0	2.43	(1.09 to 5.38)	0.03
No	676	97.7	1025	99.0	Ref
NI treatment
Yes	635	91.8	942	91.0	1.10	(0.78 to 1.55)	0.59
≤ 48h symptom onset	154	23.1	283	28.4	0.89	(0.60 to 1.30)	0.54
> 48h symptom onset	455	68.3	619	62.2	1.20	(0.84 to 1.70)	0.31
No	57	8.6	93	9.3	Ref
Number of risk factors
0	172	24.9	270	26.1	0.78	(0.58 to 1.06)	0.11
1	241	34.8	378	36.5	0.78	(0.59 to 1.04)	0.09
2	155	22.4	235	22.7	0.81	(0.62 to 1.10)	0.18
> 2	124	17.9	152	14.7	Ref
Hospital stay
0–7 days	145	21	539	52.1	0.24	(0.197 to 0.30)	< 0.001
> 7 days	545	79	145	21	Ref
Hospital stay
0–14 days	335	48.6	859	83	0.19	(0.15 to 2.41)	< 0.001
> 14 days	355	51.4	176	17	Ref

CI: confidence interval; COPD: chronic obstructive pulmonary disease; ICU: intensive care unit; NI: Neuraminidase inhibitors; OR: odds ratio; Ref: reference.