Skip to main content

Table 1 Characteristics of influenza laboratory confirmed cases (n = 331) and test-negative controls (n = 995) in the surveillance-based 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 (%)
ILI negative controls
n (%)
p valueb
Mean age (SDc) 23.4 (17.8) 25.4 (21.4) 0.125
Sex: male 162/330 (49.1) 492/984 (50.0) 0.775
Pandemic influenza vaccination 9/331 (2.7) 41/995 (4.1) 0.234
Seasonal influenza vaccination 37/330 (11.2) 104/988 (10.5) 0.727
Symptoms:    
   ▪ sudden onset 211/241 (87.5) 562/817 (68.8) < 0.0001
   ▪ fever 321/328 (97.9) 890/991 (89.8) < 0.0001
   ▪ malaise 268/315 (85.1) 713/967 (73.7) < 0.0001
   ▪ headache 251/320 (78.4) 588/964 (61.0) < 0.0001
   ▪ myalgia 213/322 (66.2) 589/978 (60.2) 0.057
   ▪ cough 295/329 (89.7) 775/985 (78.7) < 0.0001
   ▪ sore throat 224/322 (69.6) 601/970 (61.9) 0.013
   ▪ shortness of breath 27/305 (8.9) 84/948 (8.9) 0.996
At least one chronic condition 39/247 (15.8) 120/826 (14.5) 0.624
Pregnancy 5/329 (1.5) 7/976 (0.7) 0.187
Complying with EU case definition 195/331 (58.9) 506/995 (50.8) 0.011
Delay onset-swabbing less than four days 301/331 (90.9) 874/995 (87.8) 0.124
  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 test when appropriate; c SD-standard deviation.