Table 3. Details for influenza A and B in cases and control aged 65 years and older, test–negative influenza case–control study, United Kingdom, influenza seasons 2010/11–2016/17.

Characteristics	Controls	Percent	Influenza type
Characteristics	Controls	Percent	B	Percent	A(H1N1)pdm09	Percent	A(H3N2)	Percent	A (Unknown)	Percent
Scheme^a
Northern Ireland	64	65.3	4	4.1	3	3.1	20	20.4	7	7.1
RCGP (England)	831	80.9	51	5.0	36	3.5	107	10.4	2	0.2
SMN (England)	122	89.1	3	2.2	3	2.2	9	6.6	0	0.0
Scotland	652	83.3	39	5.0	11	1.4	70	8.9	11	1.4
Wales	33	64.7	4	7.8	4	7.8	9	17.6	1	2.0
Sex
Female	1,040	81.6	53	4.2	30	2.4	137	10.8	14	1.1
Male	655	80.5	48	5.9	27	3.3	77	9.5	7	0.9
Missing	7	87.5	0	0.0	0	0.0	1	12.5	0	0.0
Age group
65–74	1,084	81	76	5.7	42	3.1	124	9.3	13	1.0
75–84	487	87.2	21	3.6	12	2.0	64	10.9	5	0.8
≥ 85	131	78	4	2.4	3	1.8	27	16.1	3	1.8
Month^a
October	218	98.6	1	0.5	0	0.0	1	0.5	1	0.5
November	283	98.3	3	1.0	1	0.3	1	0.3	0	0.0
December	397	80.4	21	4.3	15	3.0	61	12.3	0	0.0
January	400	77.5	27	5.2	18	3.5	66	12.8	5	1.0
February	223	69.9	21	6.6	11	3.4	58	18.2	6	1.9
March	130	65.0	24	12.0	12	6.0	25	12.5	9	4.5
April	51	87.9	4	6.9	0	0.0	3	5.2	0	0.0
Onset of symptoms to swab^a
0–1 days	165	77.1	7	3.3	7	3.3	33	15.4	2	0.9
2–4 days	766	78.1	55	5.6	31	3.2	116	11.8	13	1.3
5–7 days	771	85.6	39	4.3	19	2.1	66	7.3	6	0.7
Influenza season^a
2010/11	222	84.7	24	9.2	16	6.1	0	0.0	0	0.0
2011/12	232	91.7	2	0.8	0	0.0	19	7.5	0	0.0
2012/13	196	73.1	32	11.9	0	0.0	38	14.2	2	0.7
2013/14	144	92.9	0	0.0	0	0.0	3	1.9	8	5.2
2014/15	249	70.9	12	3.4	1	0.3	84	23.9	5	1.4
2015/16	346	84.6	19	4.6	39	9.5	4	1.0	1	0.2
2016/17	313	78.6	12	3.0	1	0.3	67	16.8	5	1.3
Vaccination^a
Unvaccinated	551	82.4	41	6.1	28	4.2	44	6.6	5	0.7
14–91 days before onset	666	87.7	13	1.7	11	1.4	66	8.7	3	0.4
> 92 days before onset	485	72.6	47	7.0	18	2.7	105	15.7	13	1.9

RCGP: Royal College of General Practitioners Research and Surveillance Centre; SMN: specialist regional microbiology laboratories.

^a P value was < 0.001.