Effectiveness of influenza vaccine against laboratory-confirmed influenza, in the late 2011–2012 season in Spain, among population targeted for vaccination

Table 1 Characteristics of influenza A(H3N2) confirmed cases (N = 226) and test-negative controls (N = 116) in target group for vaccination, cycEVA 2011–12 study (weeks 52/2011 – 14/2012), Spain

Variables	Controls no./total no. (%)^a	A(H3N2) cases no./total no. (%)^a	P value^b
Median age (range years)	53 (3–87)	63 (3–93)	0.011
Age group (years)
0–4	4/116 (3.2)	5/226 (2.2)	0.088
5–14	8/116 (6.5)	14/226 (6.2)
15–64	69/116 (58.5)	107/226 (47.3)
≥65	35/116 (31.8)	100/226 (44.2)
Sex: male	52/116 (46.9)	106/226 (46.9)	0.716
Any chronic condition reported	73/116 (62.9)	117/226 (51.8)	0.049
Pregnancy	3/116 (2.6)	6/226 (2.6)	0.970
Obesity ^c	6/116 (4.9)	12/226 (5.3)	0.957
Any hospitalization	4/116 (3.4)	11/226 (4.9)	0.544
Median GP visits (range number)	5 (0–32)	5 (0–32)	0.782
Smoker	23/115 (19.1)	25/223 (11.2)	0.046
Swabbing less 4 days	108/116 (93.1)	217/226 (96.0)	0.240
Median time since vaccination (range days)	109 (39–151)	116 (62–166)	0.432
Vaccine coverage
By seasonal vaccine
Seasonal 2011-12	46/116 (39.7)	88/226 (38.9)	0.898
Seasonal 2010-11	40/116 (34.5)	75/224 (33.5)	0.853
By age groups
0–4 years	1/4 (25.0)	2/5 (40.0)	0.635
5–14 years	1/8 (12.5)	2/14 (14.3)	0.907
15–64 years	19/69 (27.6)	19/107 (17.8)	0.124
≥65 years	25/35 (71.4)	65/100 (65.0)	0.487

GP: general practitioners and paediatricians.
^aCases and controls recruited between weeks 52/2011 – 14/2012 and with an interval between symptom onset and swabbing of less than eight days.
^bNon parametric test of the median or Chi-square test or Fisher’s exact test, when appropriate.
^cDefined as body mass index ≥ 40 kg/m².

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