Table 1. Characteristics of the patients with medically-attended influenza-like illness included in the test-negative case–control analysis, Navarre, Spain, December 2017–January 2018 (n = 1,268 patients).

Characteristics	Test-negative controls		All influenza cases		Influenza B		Influenza A(H3N2)		Influenza A(H1N1)pdm09
Characteristics	N	%	N	%	N	%	N	%	N	%
Age groups (years)
9–24	14	2	35	5	30	6	2	2	3	8
25–44	89	15	150	23	109	22	27	22	14	39
45–64	123	20	170	26	136	27	25	21	8	22
65–84	271	44	203	31	158	32	37	32	8	22
≥ 85	117	19	96	15	65	13	27	23	3	8
Sex
Male	336	55	311	48	230	46	62	52	18	50
Female	278	45	343	52	268	54	56	48	18	50
Major chronic conditions
No	167	27	278	43	221	44	37	31	19	53
Yes	447	73	376	57	277	56	80	69	17	47
Month of swabbing
December	178	29	91	14	76	15	11	9	4	11
January	436	71	563	86	422	85	107	91	32	89
Target group for vaccination^a
No	110	18	210	32	164	33	27	23	18	50
Yes	504	82	444	68	334	67	91	77	18	50
Healthcare setting
Primary healthcare	131	21	329	50	264	53	43	37	22	61
Hospitalization	483	79	325	50	234	47	75	63	14	39
2017/18 season vaccine
No	283	46	423	65	328	66	66	56	28	78
Yes	331	54	231	35	170	34	52	44	8	22
Total	614	100	654	100^b	498	100	118	100	36	100

^a Target group for vaccination includes people ≥ 60 years-old and people with major chronic conditions.

^b Two cases were influenza A not subtyped.