Table 1. Analysis of single variables potentially associated with influenza A(H3N2) virus strain infection related deaths, Cambridge, England, 2016/17 (n = 332).

Variable	Category or measure	Expired	Not expired	OR (95% CI)	p value
Age at positive specimen (years)	Minimum	34	0	1.04 (1.01–1.06) per year	< 0.001
	25th centile	71	53
	Median	84	74
	75th centile	88	85
	Maximum	102	101
Sex	Female	13	162	Reference	0.15
	Male	19	138	1.72 (0.82–3.60)
Body mass index (BMI) ≥ 40 Kg/m2	Yes	1	5	Reference	0.6
	No	31	295	1.90 (0.22–16.8)
Pregnancy	Pregnant	0	3	0.00 (not estimable)	0.3
	Not pregnant	13	159	Reference
	Male	19	138	1.68 (0.80–3.54)
Oseltamivir course completed	1. Not given	7	66	Reference	0.7
	2. Non-standard course	3	18	1.57 (0.37–6.70)
	3. Appropriately modified	6	40	1.41 (0.44–4.51)
	4. Standard course	16	176	0.86 (0.34–2.18)
Days between onset of influenza illness and first dose of oseltamivir	Minimum	0	0	0.89 (0.74–1.06) per day delay	0.4
	25th centile	2	2
	Median	3	3
	75th centile	5	5
	Maximum	11	18
Current smoker	Yes	2	29	0.60 (0.13–2.68)	0.5
	No	23	200	Reference
Long-term oxygen therapy	Yes	1	2	4.69 (0.41–53.6)	0.3
	No	24	225	Reference
Hypertension	Yes	14	111	1.32 (0.63–2.77)	0.5
	No	18	189	Reference
Trauma	Yes	1	4	2.39 (0.26–22.0)	0.5
	No	31	296	Reference
Excessive alcohol use	Yes	3	5	6.10 (1.39–26.8)	0.03
	No	29	295	Reference
Surgery	Yes	3	13	2.28 (0.61–8.48)	0.25
	No	29	287	Reference
Immune suppressed	Yes	3	61	0.40 (0.12–1.37)	0.11
	No	29	238	Reference
Receipt of 2016/17 influenza vaccine	Yes	11	110	0.90 (0.42–1.95)	0.8
	No	21	190	Reference
Steroids	Yes	0	2	0.00 (not estimable)	0.5
	No	32	298	Reference
Chemotherapy	Yes	0	21	0.00 (not estimable)	0.04
	No	32	279	Reference
Radiotherapy	Yes	1	1	9.65 (0.59–158)	0.14
	No	31	299	Reference
Organ transplant	Yes	0	12	0.00 (not estimable)	0.12
	No	32	288	Reference
Bone marrow transplant	Yes	0	4	0.00 (not estimable)	0.4
	No	32	296	Reference
Immune deficiency syndrome	Yes	0	0	Not estimable	NA
	No	32	300	Reference
Other category of immune suppression	Yes	2	21	0.89 (0.20–3.96)	0.9
	No	30	279	Reference
Haemoglobin concentration g/L	Minimum	68	45	0.98 (0.96–0.99) per g/L	0.01
	25th centile	98.5	108
	Median	112	123
	75th centile	124	135
	Maximum	153	175
Total white cell count × 109/L	Minimum	2.1	0	QFa	0.008
	25th centile	7.7	5.3
	Median	10.1	7.3
	75th centile	14.3	9.6
	Maximum	48.5	53.6
Lymphocyte count × 109/L	Minimum	0.2	0	0.88 (0.57–1.37) per count per × 109/L	0.4
	25th centile	0.5	0.5
	Median	0.8	0.8
	75th centile	1.2	1.2
	Maximum	2.3	46.7
C-reactive protein mg/L	Minimum	5	1	1.00 (1.00–1.01)	0.01
	25th centile	26.3	19.6
	Median	64.9	39.9
	75th centile	164	76.6
	Maximum	431	479
Creatinine mmol/L	Minimum	48	8	QFb	0.002
	25th centile	69	64
	Median	99	84
	75th centile	114	111
	Maximum	187	742
Urea mmol/L	Minimum	4.5	1.6	QFc	< 0.001
	25th centile	7.2	4.6
	Median	9.2	6.2
	75th centile	11	8.6
	Maximum	18.6	39.2
Glucose mmol/L	Minimum	5.1	3.4	1.04 (0.95–1.13) per mmol/L	0.4
	25th centile	6.7	6
	Median	7.8	6.9
	75th centile	8.9	8.7
	Maximum	24	36.2
Required oxygen	Yes	8	32	2.79 (1.16–6.73)	0.03
	No	24	268	Reference
Continuous positive airways pressure	Yes	1	3	3.20 (0.32–31.6)	0.4
	No	31	297	Reference
Non-invasive ventilation	Yes	3	3	10.2 (1.98–53.1)	0.01
	No	29	297	Reference
Invasive ventilation	Yes	5	22	2.34 (0.82–6.68)	0.14
	No	27	278	Reference
Charlson comorbidity index	Minimum	0	0	1.21 (1.03–1.43)	0.03
	25th centile	2	1
	Median	2	2
	75th centile	4	3
	Maximum	8	10
Cycle threshold (CT) value	Minimum	19	16	0.96 (0.88–1.04)	0.3
	25th centile	23	27
	Median	27	30
	75th centile	32	32
	Maximum	38	41
Place of acquisition of infection	Community	15	219	Reference	0.003
	Hospital	17	81	3.06 (1.46–6.42)
Admitted from	Own home	25	251	Reference	0.5
	Residential care	4	28	1.43 (0.47–4.42)
	Another hospital	3	13	2.32 (0.62–8.68)
	Other	0	4	0.00 (not estimable)
Oseltamivir prescribed for post-exposure prophylaxis	Yes	2	8	2.43 (0.49–12.0)	0.3
	No	30	292	Reference
Pneumonia	No imaging	2	34	Reference	0.005
	No pneumonia on image	16	214	1.27 (0.28–5.78)
	Pneumonia on image	14	52	4.58 (0.98–21.4)
Myocardial infarction	Yes	6	32	1.93 (0.74–5.05)	0.2
	No	26	268	Reference
Congestive heart failure	Yes	5	33	1.50 (0.54–4.16)	0.5
	No	27	267	Reference
Peripheral vascular disease	Yes	3	8	3.78 (0.95–15.0)	0.09
	No	29	292	Reference
Cerebro vascular disease	Yes	8	47	1.79 (0.76–4.23)	0.2
	No	24	253	Reference
Dementia	Yes	8	38	2.30 (0.96–5.48)	0.08
	No	24	262	Reference
Chronic lung disease	Yes	16	88	2.41 (1.15–5.03)	0.02
	No	16	212	Reference
Connective tissue disease	Yes	2	21	0.89 (0.20–3.96)	0.9
	No	30	279	Reference
Peptic ulcer	Yes	3	6	5.07 (1.20–21.3)	0.047
	No	29	294	Reference
Mild liver disease	Yes	1	2	4.81 (0.42–54.5)	0.3
	No	31	298	Reference
Moderate or severe liver disease	Yes	3	9	3.34 (0.86–13.0)	0.11
	No	29	291	Reference
Diabetes without end organ damage	Yes	5	49	0.95 (0.35–2.58)	0.9
	No	27	251	Reference
Diabetes with end organ damage	Yes	2	15	1.27 (0.28–5.81)	0.8
	No	30	285	Reference
Hemiplegia	Yes	1	13	0.71 (0.09–5.63)	0.7
	No	31	287	Reference
Moderate or severe kidney disease	Yes	5	46	1.02 (0.37–2.79)	0.97
	No	27	254	Reference
Tumour without metastasis	Yes	3	22	1.31 (0.37–4.63)	0.7
	No	29	278	Reference
Tumour with metastasis	Yes	1	6	1.58 (0.18–13.6)	0.7
	No	31	294	Reference
Leukaemia	Yes	0	11	0.00 (not estimable)	0.13
	No	32	289	Reference
Lymphoma	Yes	0	16	0.00 (not estimable)	0.07
	No	32	284	Reference

OR: odds ratio; CI: confidence interval; QF: quadratic function; NA: not applicable.

^a QF: linear part OR: 1.28 (95% CI: 1.11–1.47); quadratic part OR: 1.00 (95% CI: 0.99–1.00).

^b QF: linear part OR: 1.05 (95% CI: 1.01–1.09); quadratic part OR: 1.00 (95% CI: 1.00–1.00).

^c QF: linear part OR: 2.45 (95% CI: 1.48–4.06); quadratic part OR: 0.97 (95% CI: 0.94–0.99).