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Table 3 Characteristics of included patients according to PCR result

From: Influenza epidemiology and influenza vaccine effectiveness during the 2014–2015 season: annual report from the Global Influenza Hospital Surveillance Network

  Influenza-negative Influenza-positive A(H1N1)pdm09 A(H3N2) B/Yamagata lineage
  N = 7437 N = 2177 N = 115 N = 1231 N = 646
  n % n % P vs. negative n % P vs. negative n % P vs. negative n % P vs. negative
Age in years, median (range) 18.4 (0–106)   32.8 (0–100)   0.0001 5.6 (0–85)   0.0861 54.5 (0–100)   0.0001 26.2 (0–96)   0.0013
Age group      <0.0001    <0.0001    <0.0001    <0.0001
 0–1 y 1371 18.4 144 6.6   14 12.2   74 6.0   37 5.7  
 2–4 y 1777 23.9 429 19.7   36 31.3   212 17.2   133 20.6  
 5–17 y 547 7.4 280 12.9   14 12.2   121 9.8   118 18.3  
 18–49 y 1038 14 423 19.4   28 24.3   183 14.9   168 26.0  
 50–64 y 557 7.5 191 8.8   9 7.8   92 7.5   73 11.3  
 65–74 y 608 8.2 211 9.7   5 4.3   153 12.4   45 7.0  
 75–84 y 933 12.5 294 13.5   8 7.0   235 19.1   38 5.9  
 ≥85 606 8.1 205 9.4   1 0.9   161 13.1   34 5.3  
Sex      <0.0001    0.0390    0.0003    0.0040
 Male 4276 57.5 1141 52.4   55 47.8   651 52.9   333 51.5  
 Female 3161 42.5 1036 47.6   60 52.2   580 47.1   313 48.5  
Chronic conditions      0.0940    0.1600    <0.0001    0.004
 0 4572 61.5 1295 59.5   78 67.8   643 52.2   434 67.2  
 ≥1 2865 38.5 882 40.5   37 32.2   588 47.8   212 32.8  
Underlying chronic conditions
 Cardiovascular disease 1529 20.6 469 21.5 0.3210 18 15.7 0.1820 319 25.9 <0.0001 109 16.9 0.02200
 Chronic obstructive pulmonary disease 1153 15.5 306 14.1 0.0570 7 6.1 0.0001 222 18.0 0.0270 60 9.3 <0.0001
 Asthma 346 4.7 100 4.6 0.9080 5 4.3 0.8760 65 5.3 0.3440 24 3.7 0.2600
 Immunodeficiency/organ transplant 92 1.2 14 0.6 0.0130 0 0.0 0.0920 8 0.6 0.0550 6 0.9 0.4750
 Diabetes 814 10.9 234 10.7 0.7960 8 7.0 0.1480 180 14.6 <0.0001 34 5.3 <0.0001
 Renal impairment 463 6.2 143 6.6 0.5640 2 1.7 0.0200 108 8.8 0.0010 27 4.2 0.0280
 Neuromuscular disease 215 2.9 52 2.4 0.2020 8 7.0 0.0290 19 1.5 0.0040 22 3.4 0.4670
 Neoplasm 238 3.2 63 2.9 0.4660 4 3.5 0.8680 38 3.1 0.8330 17 2.6 0.4160
 Cirrhosis/liver disease 168 2.3 34 1.6 0.0390 0 0.0 0.0220 19 1.5 0.0950 11 1.7 0.3390
 Autoimmune disease 127 1.7 48 2.2 0.1360 1 0.9 0.4470 36 2.9 0.0060 8 1.2 0.3510
Pregnant (women 15–45 y) 138 33.7 160 64.8 0.0000 11 68.8 0.0050 64 55.7 <0.0001 68 70.1 <0.0001
Obese (all ages) 1300 17.5 358 16.4 0.2590 15 13.0 0.1970 223 18.1 0.5890 92 14.2 0.0320
Smoking habits (patients ≥18 y)
 Never smoked 1760 47.0 717 54.2   23 45.1   451 54.7   191 53.4  
 Past smoker 1164 31.1 380 28.7   14 27.5   252 30.6   96 26.8  
 Current smoker 818 21.9 227 17.1   14 27.5   121 14.7   71 19.8  
Functional status impairment (Barthel score; patients ≥65 y)
 Total (0–15) 152 7.2 47 6.7   0 0.0   41 7.6   5 4.3  
 Severe (20–35) 76 3.6 19 2.7   0 0.0   13 2.4   4 3.5  
 Moderate (40–55) 140 6.7 46 6.6   0 0.0   32 5.9   11 9.6  
 Mild (60–90) 518 24.7 148 21.1   1 7.1   111 20.5   32 27.8  
 Minimal (95–100) 1214 57.8 441 62.9   13 92.9   345 63.7   63 54.8  
Influenza vaccination ≥14 d since onset of symptoms 1566 21.1 447 20.5 0.5960 6 5.2 <0.0001 356 28.9 <0.0001 57 8.8 <0.0001
  1. Not subtyped A and B were 24 patients with mixed influenza infections were not included in the analysis by strain