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Table 2 Factors influencing hospitalisation of individuals affected by pandemic influenza (H1N1) 2009 and risk factors for the development of pneumonia.

From: The first wave of pandemic influenza (H1N1) 2009 in Germany: From initiation to acceleration

Independent variables n Individuals hospitalised/with pneumonia (%) Univariate analysis OR (95%CI) p-value Multivariate analysis OR (95%CI) p- value
Hospitalisation       
   Pneumonia 275 130 (47.3) 25.5 (20.0;32.5) <0.001 18.2 (13.6;23.9) <0.001
   No pneumonia reported 40,236 1,366 (3.4) reference    
   Risk factors present 2,342 284 (12.1) 4.6 (3.6;4.7) <0.001 3.6 (3.1;4.3) <0.001
   No risk factor reported 37,187 1,215 (3.3) Reference    
   Chronic disease 2,250 261 (11.6) 3.8 (3.3;4.4) <0.001   
   No chronic disease reported 37,298 1,240 (3.3) Reference    
Immunosuppression 112 30 (26.8) 10.8 (7.1;16.3) <0.001   
No risk factor reported 37,187 1,215 (3.3) reference    
Respiratory disease 1,072 87 (8.1) 2,6 (2,1; 3,3) <0.001   
No risk factor reported 37,187 1,215 (3.3) reference    
Obesity* 159 19 (11.9) 4.0 (2,5; 6,5) <0.001   
No risk factor reported 37,187 1,215 (3.3) reference    
Cardio-vascular disease 260 34 (13.1) 4.5 (3.1; 6.4) <0.001   
No risk factor reported 37,187 1,215 (3.3) reference    
Diabetes 172 19 (11.0) 3.7 (2.3; 5.9) <0.001   
No risk factor reported 37,187 1,215 (3.3) reference    
Other chronic disease 70 70 (15.4) 5.4 (4.1; 7.0) <0.001   
No risk factor reported 37,187 1,215 (3.3) reference    
   Pregnancy 106 25 (25.6) 9.9 (6.1;16.0) <0.001   
   No pregnancy reported 16,957 527 (3.1) reference    
   Age       
0 - 2 years 920 107 (11.6) 3.3 (2.7;4.1) <0.001 2.9 (2.2;3.8) <0.001
All other age groups 51,563 1,977 (3.8) reference    
3 - 14 years 17,486 509 (2.9) 0,6 (0.5;0.7) <0.001 0.7 (0.6;0.8) <0.001
All other age groups 34,997 1,575 (4.5) reference    
   Male 27,345 1,114 (4.1) 1.1 (0.9;1.2) = 0.069 1.1 (0.9;1.2) = 0.224
   Female 24,628 927 (3.8) reference    
   Acceleration period 28,820 967 (3.4) 0.7 (0.6; 0.8) <0.001 0.8 (0.7;0.9) = 0.020
   Initiation period 23,663 1,117 (4.7) reference    
Pneumonia       
   Risk factors 2,162 76 (3.5) 7.4 (5.7;9.8) <0.001 8.1 (6.1;10.7) <0.001
   No risk factor reported 36,305 177 (0.5) reference    
   Chronic disease 2,082 75 (3.6) 7.6 (5.8;9.9) <0.001   
   No chronic disease reported 36,402 179 (0.5) reference    
Immunosuppression 103 7 (6.8) 14.9 (6.9;32.7) <0.001   
No risk factor reported 36,305 177 (0.5) reference    
Respiratory disease 994 34 (3.4) 7.2 (4.9;10.5) <0.001   
No risk factor reported 36,305 177 (0.5) reference    
Obesity* 143 9 (6.3) 13.8 (6.9;27.5) <0.001   
No risk factor reported 36,305 177 (0.5) reference    
Cardio-vascular disease 243 5 (2.1) 4.3 (1.7;10.4) = 0.002   
No risk factor reported 36,305 177 (0.5) reference    
Diabetes 157 1 (0.6) 1.3 (0.2;9.4) = 0.790   
No risk factor reported 36,305 177 (0.5) reference    
Other chronic disease 425 18 (4.2) 9.1 (5.5;14.8) <0.001   
No risk factor reported 36,305 177 (0.5) reference    
Pregnancy 95 2 (2.1) 4.6 (1.1;19.0) = 0.074   
No pregnancy reported 17,194 80 (0.5) reference    
   Age       
0 - 2 years 712 15 (2.1) 3.3 (1.9;5.5) <0.001 2,8 (1.5;5.2) <0.001
All other age groups 40,019 261 (0.7) reference    
3 - 14 years 13,453 92(0.7) 1.1 (0.8;1.3) = 0.914   
All Other age groups 27,278 184 (0.7) reference    
   Male 21,158 146 (0.7) 1.1 (0.7;1.4) = 0.413 1.1 (0.8;1.4) = 0.545
   Female 19,228 120 (0.6) reference    
   Acceleration period 22,640 182 (0.8) 1.6 (1.2;2.0) = 0.001 1.3 (1.0;1.7) = 0.038
   Initiation period 18,081 94 (0.5) reference    
   ILI** 4,442 39 (0.9) 1.3 (1.0;1.8) = 0.090 1.4 (1.0;2.1) = 0.032
   No ILI 36,289 237 (0.7) reference    
   Fever (>38.5°C) 34,905 258 (0.7) 1.9 (1.2;3.1) = 0.007 2.0 (1.2;3.5) = 0.013
   No fever reported 4,826 18 (0.4) reference    
  1. * Obesity requiring treatment or body mass index > 30
  2. ** ILI: acute onset of symptoms and fever and cough and headache or musculoskeletal pain