Background
Methods
Aims and objectives
Study design
Subjects
Data
Hospital discharge data
Influenza activity data
Temperature data
Demographic data
Outcomes
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Total number of hospitalizations associated with influenza: this is given by the sum of “observed” hospitalizations due to influenza, i.e., those recorded with primary ICD9 code 487, and “excess” hospitalizations, that are those estimated by the model described in “Data analysis” section, that are hospitalizations recorded with primary ICD9 codes different from 487, but considered associated with influenza based on the model assumptions.
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Cost of hospitalisations associated with influenza: this is an approximated estimate since it refers to excess (i.e., estimated) rather than observed hospitalisations. Hence, we hypothesised a range of possible attributable costs, ranging from prudential estimates, i.e., attributing to hospitalizations associated with influenza the same cost of hospitalizations coded with primary diagnosis influenza, to wide scope-estimates considered more realistic, where the average cost of hospitalizations for cardio-respiratory diagnoses is attributed to hospitalizations associated with influenza. See “Economic burden of hospitalisations associated with influenza” section.
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Total in-hospital mortality associated with influenza: this is given by the sum of “observed” in-hospital deaths for hospitalizations due to influenza, i.e., those deaths recorded in hospitalizations with primary ICD9 code 487, and in-hospital deaths attributable to influenza, that are those estimated by the model described in “Data analysis” section, that come from hospitalizations recorded with primary ICD9 codes different from 487, but considered associated with influenza based on the model assumptions.
Data analysis
Hospitalisations associated with influenza
Economic burden of hospitalisations associated with influenza
In-hospital mortality associated with influenza
Patient and public involvement
Results
Hospitalisations associated with influenza
Observed hospitalizations for influenza
Seasona | Total | 0–4 years | 5–14 years | 15–64 years | ≥ 65 years |
---|---|---|---|---|---|
2008/09 | 2.5 | 6.6 | 4.8 | 2.0 | 1.2 |
2009/10 | 3.3 | 8.1 | 9.2 | 2.3 | 0.9 |
2010/11 | 3.5 | 9.1 | 7.00 | 2.9 | 1.0 |
2011/12 | 3.0 | 7.9 | 4.5 | 2.6 | 1.3 |
2012/13 | 3.6 | 9.1 | 6.7 | 3.2 | 1.3 |
2013/14 | 2.7 | 7.4 | 4.2 | 2.5 | 1.1 |
2014/15 | 3.7 | 8.9 | 6.0 | 3.5 | 1.6 |
2015/16 | 2.9 | 7.9 | 5.7 | 2.4 | 1.0 |
2016/17 | 3.2 | 8.0 | 4.6 | 3.0 | 1.8 |
2017/18 | 5.1 | 13.5 | 7.4 | 4.7 | 2.6 |
2018/19 | 4.8 | 13.1 | 6.9 | 4.5 | 2.2 |
11-season mean | 3.5 | 9.0 | 6.1 | 3.0 | 1.5 |
3-season meanb | 4.4 | 11.5 | 6.3 | 4.07 | 2.2 |
Seasona | Influenza (ICD9 diagnosis 487) | All ICD9 codes associated with influenzab | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
0–4 years | 5–14 years | 15–64 years | ≥ 65 years | Total | 0–4 years | 5–14 years | 15–64 years | ≥ 65 years | Total | ||
2008/09 | N | 1,095 | 463 | 1,028 | 815 | 3,404 | 72,886 | 20,882 | 340,084 | 1,048,895 | 1,483,008 |
Ratec | 39.0 | 8.4 | 2.6 | 6.8 | 5.7 | 2,595.9 | 377.5 | 874.0 | 8,769.0 | 2,504.6 | |
2009/10 | N | 2,468 | 1,565 | 4,092 | 918 | 9,054 | 71,147 | 23,945 | 347,086 | 1,053,095 | 1,495,772 |
Rate | 87.5 | 28.1 | 10.5 | 7.6 | 15.2 | 2,521.7 | 429.7 | 888.4 | 8,708.3 | 2,511.6 | |
2010/11 | N | 1,163 | 577 | 1,523 | 759 | 4,022 | 67,592 | 22,396 | 335,004 | 1,026,908 | 1,451,913 |
Rate | 41.3 | 10.3 | 3.9 | 6.2 | 6.7 | 2,398.2 | 399.3 | 854.9 | 8,414.4 | 2,427.2 | |
2011/12 | N | 906 | 277 | 742 | 706 | 2,631 | 59,412 | 17,114 | 313,565 | 1,020,906 | 1,411,006 |
Rate | 32.4 | 4.9 | 1.9 | 5.7 | 4.4 | 2,122.4 | 303.6 | 799.9 | 8,241.8 | 2,350.6 | |
2012/13 | N | 1,189 | 442 | 1,058 | 760 | 3,449 | 57,617 | 17,577 | 307,113 | 992,889 | 1,375,196 |
Rate | 42.9 | 7.8 | 2.7 | 6.0 | 5.7 | 2,078.0 | 310.4 | 784.9 | 7,861.1 | 2,284.7 | |
2013/14 | N | 970 | 343 | 638 | 496 | 2,447 | 54,658 | 19,873 | 297,979 | 988,950 | 1,361,461 |
Rate | 35.5 | 6.0 | 1.6 | 3.9 | 4.1 | 1,998.7 | 349.8 | 763.3 | 7,690.0 | 2,257.4 | |
2014/15 | N | 1,171 | 408 | 1,162 | 1,066 | 3,807 | 55,362 | 18,429 | 298,718 | 1,004,708 | 1,377,221 |
Rate | 43.8 | 7.2 | 3.0 | 8.1 | 6.3 | 2,070.6 | 324.1 | 768.3 | 7,681.0 | 2,283.2 | |
2015/16 | N | 830 | 372 | 680 | 600 | 2,482 | 52,595 | 16,794 | 291,492 | 991,361 | 1,352,242 |
Rate | 31.9 | 6.6 | 1.8 | 4.5 | 4.1 | 2,021.5 | 296.1 | 753.1 | 7,481.1 | 2,245.1 | |
2016/17 | N | 756 | 290 | 768 | 1,314 | 3,128 | 52,248 | 15,683 | 283,149 | 986,112 | 1,337,192 |
Rate | 29.9 | 5.1 | 2.0 | 9.8 | 5.2 | 2,067.2 | 278.0 | 734.4 | 7,363.7 | 2,224.4 | |
2017/18 | N | 1,331 | 447 | 1,196 | 1,622 | 4,596 | 49,981 | 14,732 | 284,626 | 971,698 | 1,321,038 |
Rate | 54.3 | 8.0 | 3.1 | 12.0 | 7.7 | 2,037.7 | 262.8 | 740.6 | 7,190.5 | 2,201.6 | |
2018/19 | N | 1,115 | 355 | 1,331 | 1,841 | 4,642 | 50,224 | 17,164 | 284,540 | 968,675 | 1,320,630 |
Rate | 46.9 | 6.4 | 3.5 | 13.5 | 7.8 | 2,113.3 | 308.7 | 742.7 | 7,107.4 | 2,205.6 | |
Total | N | 12,994 | 5,539 | 14,218 | 10,897 | 43,662 | 643,722 | 204,589 | 3,383,356 | 11,054,197 | 15,286,679 |
11-season mean | N | 1,181.3 | 503.5 | 1,292.5 | 990.6 | 3,969.3 | 58,520.2 | 18,599.0 | 307,577.8 | 1,004,927.0 | 1,389,698.1 |
Rate | 44.2 | 9.0 | 3.3 | 7.7 | 6.6 | 2,190.5 | 330.7 | 791.6 | 7,839.7 | 2,317.4 | |
3-season meand | N | 1,067.3 | 364.0 | 1,098.3 | 1,592.3 | 4,122.0 | 50,817.7 | 15,859.7 | 284,105.0 | 975,495.0 | 1,326,286.7 |
Rate | 40.0 | 6.5 | 2.8 | 12.4 | 6.9 | 1,902.2 | 282.0 | 731.2 | 7,610.1 | 2,211.6 |
Excess hospitalisations associated with influenza
Seasona | 0–4 years | 5–14 years | 15–64 years | ≥ 65 years | Total | |||||
---|---|---|---|---|---|---|---|---|---|---|
N | Rateb | N | Rateb | N | Rateb | N | Rateb | N | Rateb | |
2008/09 | 2207 | 78.6 | 666 | 12.0 | 3171 | 8.2 | 13971 | 116.8 | 16,503 | 27.9 |
2009/10 | 1932 | 68.5 | 1193 | 21.4 | 3203 | 8.2 | 10042 | 83.0 | 20,613 | 34.8 |
2010/11 | 2749 | 97.5 | 941 | 16.8 | 4275 | 10.9 | 10895 | 89.3 | 22,797 | 38.5 |
2011/12 | 2315 | 82.7 | 585 | 10.4 | 3771 | 9.6 | 14937 | 120.6 | 18,966 | 32.0 |
2012/13 | 2535 | 91.4 | 851 | 15.0 | 4536 | 11.6 | 14791 | 117.1 | 23,241 | 39.3 |
2013/14 | 1871 | 68.4 | 480 | 8.4 | 3416 | 8.8 | 12418 | 96.6 | 16,849 | 28.5 |
2014/15 | 2197 | 82.2 | 696 | 12.2 | 4759 | 12.2 | 18070 | 138.1 | 22,885 | 38.7 |
2015/16 | 1788 | 68.7 | 632 | 11.1 | 3212 | 8.3 | 10453 | 78.9 | 17,203 | 29.1 |
2016/17 | 1756 | 69.5 | 467 | 8.3 | 3950 | 10.2 | 19295 | 144.1 | 19,073 | 32.2 |
2017/18 | 2988 | 121.8 | 763 | 13.6 | 6069 | 15.8 | 28959 | 214.3 | 30,556 | 51.6 |
2018/19 | 2767.7 | 116.5 | 701 | 12.6 | 5679 | 14.8 | 23542 | 172.7 | 28,211 | 47.6 |
Total | 25,106 | 7,975 | 46,042 | 177,373 | 236,896 | |||||
11-season mean | 2282 | 86.0 | 725 | 12.9 | 4186 | 10.8 | 16125 | 124.7 | 21536 | 36.4 |
3-season meanc | 2503.9 | 102.6 | 643.7 | 11.5 | 5232.7 | 13.6 | 23932 | 177.0 | 25946.7 | 43.8 |
Economic burden of hospitalisations associated with influenza
Seasona | Influenza (ICD9 code 487, primary) | Cardiorespiratory diseasesc | ||
---|---|---|---|---|
Average length of stay (days) | Average cost (€) | Average length of stay (days) | Average cost (€) | |
2008/09 | 4.9 | 1581.1 | 10.3 | 4093.4 |
2009/10 | 5.1 | 2224.9 | 10.3 | 4979.8 |
2010/11 | 5.2 | 2221.4 | 10.3 | 5091.0 |
2011/12 | 5.1 | 1646.2 | 10.3 | 5166.1 |
2012/13 | 5.2 | 1985.5 | 10.3 | 5211.5 |
2013/14 | 4.7 | 1822.9 | 10.3 | 5258.0 |
2014/15 | 5.5 | 2822.4 | 10.4 | 5350.5 |
2015/16 | 5.6 | 2214.6 | 10.5 | 5444.7 |
2016/17 | 5.8 | 1956.6 | 10.4 | 5463.4 |
2017/18 | 6.1 | 2776.1 | 10.5 | 5497.5 |
2018/19 | 6.7 | 2496.9 | 10.5 | 5560.8 |
11-season mean | 5.5 | 2159.0 | 10.4 | 5192.4 |
3-season meanb | 6.2 | 2409.9 | 11.1 | 4856.9 |
In-hospital mortality associated with influenza
Seasona | Influenza (ICD9 diagnosis 487) | All ICD9 associated with influenza | ||||||||
---|---|---|---|---|---|---|---|---|---|---|
0–4 years | 5–14 years | 15–64 years | ≥ 65 years | Total | 0–4 years | 5–14 years | 15–64 years | ≥ 65 years | Total | |
2008/09 | 0 | 0 | 1 | 14 | 15 | 153 | 61 | 6,674 | 71,286 | 78,184 |
2009/10 | 0 | 3 | 48 | 25 | 76 | 125 | 57 | 6,896 | 72,227 | 79,319 |
2010/11 | 0 | 0 | 44 | 19 | 63 | 130 | 68 | 7,057 | 72,410 | 79,666 |
2011/12 | 0 | 0 | 3 | 13 | 16 | 127 | 52 | 6,756 | 75,940 | 82,875 |
2012/13 | 0 | 0 | 8 | 15 | 23 | 113 | 69 | 6,792 | 72,943 | 79,917 |
2013/14 | 0 | 0 | 2 | 5 | 7 | 120 | 64 | 6,408 | 72,655 | 79,247 |
2014/15 | 0 | 0 | 34 | 55 | 89 | 112 | 61 | 7,000 | 79,204 | 86,377 |
2015/16 | 0 | 0 | 12 | 13 | 25 | 114 | 71 | 6,720 | 77,371 | 84,276 |
2016/17 | 0 | 0 | 8 | 49 | 57 | 114 | 59 | 6,790 | 81,387 | 88,350 |
2017/18 | 0 | 1 | 17 | 47 | 65 | 127 | 81 | 6,845 | 78,976 | 86,029 |
2018/19 | 1 | 0 | 22 | 94 | 117 | 105 | 60 | 6,720 | 79,739 | 86,624 |
Total | 1 | 4 | 199 | 349 | 553 | 1,339 | 703 | 74,658 | 834,138 | 910,864 |
11-season mean | 0 | 0.4 | 17.7 | 25.5 | 50.3 | 123.5 | 64.3 | 6,793.8 | 75,439.9 | 82,805.8 |
3-season meanb | 0.3 | 0.3 | 15.7 | 63.3 | 79.7 | 115.3 | 66.7 | 6785 | 80034 | 87001 |
Seasona | 0–4 years | 5–14 years | 15–64 years | ≥ 65 years | Total | |||||
---|---|---|---|---|---|---|---|---|---|---|
N | Rateb | N | Rate | N | Rate | N | Rate | N | Rate | |
2008/09 | 4 | 0.1 | 3 | 0.0 | 253 | 0.6 | 3157 | 26.4 | 2,424 | 4.1 |
2009/10 | 4 | 0.1 | 6 | 0.1 | 267 | 0.7 | 2271 | 18.8 | 3,196 | 5.4 |
2010/11 | 5 | 0.2 | 4 | 0.1 | 358 | 0.9 | 2517 | 20.6 | 3,553 | 5.9 |
2011/12 | 4 | 0.1 | 3 | 0.0 | 319 | 0.8 | 3555 | 28.7 | 2,985 | 5.0 |
2012/13 | 4 | 0.2 | 4 | 0.1 | 393 | 1.0 | 3568 | 28.2 | 3,764 | 6.3 |
2013/14 | 3 | 0.1 | 2 | 0.0 | 297 | 0.8 | 3045 | 23.7 | 2,771 | 4.6 |
2014/15 | 4 | 0.2 | 4 | 0.1 | 432 | 1.1 | 4594 | 35.1 | 3,900 | 6.5 |
2015/16 | 3 | 0.1 | 4 | 0.1 | 286 | 0.7 | 2614 | 19.7 | 2,941 | 4.9 |
2016/17 | 3 | 0.1 | 3 | 0.1 | 372 | 1.0 | 5214 | 38.9 | 3,393 | 5.6 |
2017/18 | 69 | 0.2 | 5 | 0.1 | 602 | 1.6 | 8176 | 60.5 | 5,700 | 9.5 |
2018/19 | 6 | 0.2 | 5 | 0.1 | 563 | 1.5 | 6489 | 47.6 | 5,313 | 8.9 |
Total | 46 | 42 | 4,141 | 45,199 | 39,941 | |||||
11-season mean | 4 | 0.2 | 4 | 0.1 | 377 | 1.0 | 4,109 | 31.7 | 3,631 | 6.1 |
3-season meanc | 26 | 0.2 | 4.3 | 0.1 | 512.3 | 1.4 | 6626.3 | 49 | 4802 | 8 |