Table 3 Characteristics of influenza laboratory confirmed cases (n = 85) and test-negative controls (n = 351) in the cycEVA study^a, season 2009-2010, Spain

Mean age (SD^c)

33.2 (17.9)

35.9 (20.0)

0.256

Sex: male

34/85 (40.0)

174/350 (49.7)

0.108

Pandemic influenza vaccination

2/85 (2.4)

19/351 (5.4)

0.395

Seasonal influenza vaccination

9/84 (10.7)

45/347 (12.9)

0.714

Symptoms:

   ▪ sudden onset

80/84 (95.2)

322/342 (94.2)

0.699

   ▪ fever

83/84 (98.8)

321/337 (95.3)

0.138

   ▪ malaise

77/79 (97.5)

305/317 (96.2)

0.589

   ▪ headache

70/78 (89.7)

254/310 (81.9)

0.097

   ▪ myalgia

63/79 (79.8)

275/316 (87.0)

0.100

   ▪ cough

76/82 (92.7)

268/332 (80.7)

0.010

   ▪ sore throat

58/81 (71.6)

239/315 (75.9)

0.429

   ▪ shortness of breath

9/74 (12.2)

23/266 (8.6)

0.371

Previous vaccination

9/78 (11.5)

45/300 (15.0)

0.586

Smoking

3/72 (4.2)

18/277 (6.5)

0.586

Any hospitalization

2/75 (2.7)

5/279 (1.8)

0.643

GP visits > eight in the previous year

16/74 (21.6)

68/282 (24.1)

0.653

Any chronic conditions

6/83 (7.2)

53/332 (15.9)

0.052

Pregnancy and obesity

7/84 (8.3)

26/348 (7.5)

0.819

Poor functional status

1/80 (1.3)

18/337 (5.3)

0.143

Complying with EU case definition

77/85 (90.6)

300/351 (85.5)

0.215

Delay onset-swabbing less than four days

80/85 (94.1)

301/351 (85.8)

0.037