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Table 5 Characteristics of patients included in the IVE analysis by vaccination status

From: Influenza epidemiology and influenza vaccine effectiveness during the 2015–2016 season: results from the Global Influenza Hospital Surveillance Network

Risk variable Category Unvaccinated Vaccinated P value
Number of patients, n (%) Controls 5452 (72.9) 1250 (83.6) <  0.001
Cases 2023 (27.1) 246 (16.4)  
Age (y) Median (IQR) 19.3 (3.0–51.9) 74.8 (56.3–83.3) <  0.001
Age group, n (%) 6–11 months 524 (7.0) 14 (0.9) <  0.001
1–4 y 2370 (31.7) 76 (5.1)  
5–17 y 758 (10.1) 136 (9.1)  
18–49 y 1879 (25.1) 114 (7.6)  
50–64 y 726 (9.7) 114 (7.6)  
65–74 y 487 (6.5) 302 (20.2)  
75–84 y 513 (6.9) 438 (29.3)  
≥ 85 y 218 (2.9) 302 (20.2)  
Female, n (%) 3480 (46.6) 637 (42.6) 0.005
Comorbidities, n (%) No 5350 (71.6) 415 (27.7) <  0.001
Yes 2125 (28.4) 1081 (72.3)  
Pregnant (women 15–45 y), n (%) 606 (59.4) 8 (29.6) 0.002
Obesea, n (%) 1038 (13.9) 321 (21.5) <  0.001
Hospitalization within ≤12 mo, n (%) 1954 (26.1) 549 (36.7) <  0.001
Outpatient consultations within ≤3 mo, n (%) No 2624 (35.11) 304 (20.32) <  0.001
Yes 4850 (64.89) 1192 (79.68)  
Smoking (≥ 18 y), n (%) Current 949 (25.0) 186 (14.7) <  0.001
Past 924 (24.3) 475 (37.5)  
Never 1926 (50.7) 605 (47.8)  
Functional impairment (≥ 65 y), n (%) None or minimal 471 (46.0) 572 (58.3) <  0.001
Mild 321 (31.4) 232 (23.7)  
Moderate 98 (9.6) 54 (5.5)  
Severe 38 (3.7) 39 (4.0)  
Total 95 (9.3) 84 (8.6)  
Sampling interval (d) Median (IQR) 3 (2–5) 4 (2–5) <  0.001
Sampling interval, n (%) ≤ 4 d 5139 (68.8) 920 (61.5)  
5–7 d 2104 (28.2) 475 (31.8)  
8–9 d 232 (3.1) 101 (6.8)  
Site, n (%) St. Petersburg 1645 (22.0) 45 (3.0) <  0.001
Moscow 1808 (24.2) 87 (5.8)  
Czech Republic 115 (1.5) 7 (0.5)  
France 81 (1.1) 60 (4.0)  
Turkey 522 (7.0) 43 (2.9)  
Beijing 1854 (24.8) 258 (17.3)  
Valencia 1018 (13.6) 931 (62.2)  
India 259 (3.5) 15 (1.0)  
Mexico 87 (1.2) 5 (0.3)  
Curitiba 86 (1.2) 45 (3.0)  
Vaccinated, n (%) In 2013–2014 526 (7.1) 1073 (72.8) <  0.001
In 2014–2015 545 (7.4) 1200 (81.2) <  0.001
  1. aDetermined from the body mass index according to age and sex following the World Health Organization guidelines [12]