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

From: Using surveillance data to estimate pandemic vaccine effectiveness against laboratory confirmed influenza A(H1N1)2009 infection: two case-control studies, Spain, season 2009-2010

Characteristics Cases
n (%)
Controls
n (%)
p valueb
Mean age (SDc) 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
  1. a Cases and controls recruited between week 48/2009 and week 8/2010 and with a delay symptom onset-swabbing less than eight days; b Chi square or Fisher exact tests when appropriate; c SD-standard deviation.