Demographic and clinical characteristics of cases and controls and by influenza vaccination status in the total sample during the 2015–2016 influenza season
| Influenza test result | SIV in 2015–2016 | |||||||||
| Influenza-positive n=72 44.2% | Influenza-negative n=91 55.8% | p Value | Vaccinated n=15 9.2% | Unvaccinated n=148 90.8% | p-Value | |||||
| N | % | N | % | N | % | n | % | |||
| Male sex | 30 | 41.7 | 46 | 50.5 | 0.27 | 10 | 66.7 | 66 | 44.6 | 0.11 |
| Urban | 56 | 77.8 | 72 | 79.1 | 0.85 | 9 | 60.0 | 119 | 80.4 | 0.09 |
| Age≥65 | 32 | 44.4 | 59 | 64.8 | 0.01 | 12 | 80.0 | 79 | 53.4 | 0.06 |
| Age (mean, SD) | 59.1 | 19.2 | 67.1 | 17.2 | 0.01 | 72.9 | 10.1 | 62.6 | 18.9 | 0.04 |
| Education | ||||||||||
| High (college, university) | 29 | 42.0 | 36 | 39.6 | 0.81 | 7 | 46.7 | 58 | 40.0 | 0.78 |
| Low (primary, unfinished, secondary, professional) | 40 | 58.0 | 55 | 60.4 | 8 | 53.3 | 87 | 60.0 | ||
| Occupation | ||||||||||
| Intellectual or/and physical work | 17 | 23.6 | 19 | 20.9 | 0.71 | 1 | 6.7 | 35 | 23.6 | 0.19 |
| Retired/handicapped/jobless | 55 | 76.4 | 72 | 79.1 | 14 | 93.3 | 113 | 76.4 | ||
| Income per household member | ||||||||||
| <€600 | 57 | 91.9 | 75 | 97.4 | 0.24 | 13 | 92.9 | 119 | 95.2 | 0.53 |
| ≥€600 | 5 | 8.1 | 2 | 2.6 | 1 | 7.1 | 6 | 4.8 | ||
| Smoking | ||||||||||
| Never | 35 | 49.3 | 45 | 49.5 | 0.48 | 7 | 46.7 | 73 | 49.7 | 0.52 |
| Former | 23 | 32.4 | 35 | 38.5 | 7 | 46.7 | 51 | 34.7 | ||
| Current | 13 | 18.3 | 11 | 12.1 | 1 | 6.7 | 23 | 15.6 | ||
| Pregnant | 10 | 13.9 | 1 | 1.1 | 0.003 | 0 | 0.0 | 11 | 7.4 | 0.60 |
| Chronic condition (at least 1) | 60 | 83.3 | 87 | 95.6 | 0.02 | 13 | 86.7 | 134 | 90.5 | 0.65 |
| At least one hospitalisation due to exacerbation of underlying conditions in the previous 12 months | 13 | 21.7 | 37 | 42.5 | 0.01 | 7 | 53.8 | 43 | 32.1 | 0.13 |
| At least 1 GP visit in the previous 12 months | 24 | 34.8 | 35 | 38.9 | 0.62 | 3 | 21.4 | 56 | 38.6 | 0.26 |
| Cardiovascular disease | 34 | 47.2 | 59 | 64.8 | 0.03 | 10 | 66.7 | 83 | 56.1 | 0.58 |
| Lung diseases | 10 | 13.9 | 32 | 35.2 | 0.002 | 4 | 26.7 | 38 | 25.7 | 1.00 |
| Endocrine diseases, diabetes | 6 | 8.3 | 18 | 19.8 | 0.05 | 3 | 20.0 | 21 | 14.2 | 0.47 |
| Renal diseases | 5 | 6.9 | 9 | 9.9 | 0.58 | 1 | 6.7 | 13 | 8.8 | 1.00 |
| Immunodeficiency and transplantations | 5 | 6.9 | 1 | 1.1 | 0.09 | 0 | 0.0 | 6 | 4.1 | 1.00 |
| Rheumatological diseases | 2 | 2.8 | 2 | 2.2 | 1.00 | 0 | 0.0 | 4 | 2.7 | 1.00 |
| Dementia, strokes | 11 | 15.3 | 26 | 28.6 | 0.06 | 5 | 33.3 | 32 | 21.6 | 0.33 |
| Haematological cancer | 4 | 5.6 | 4 | 4.4 | 0.73 | 1 | 6.7 | 7 | 4.7 | 0.55 |
| Non-haematological cancer | 9 | 12.5 | 15 | 16.5 | 0.51 | 3 | 20.0 | 21 | 14.2 | 0.47 |
| Anaemia, spleen | 3 | 4.2 | 6 | 6.6 | 0.73 | 2 | 13.3 | 7 | 4.7 | 0.20 |
| Cirrhosis | 0 | 0 | 0 | 0 | – | 0 | 0 | 0 | 0 | – |
| Nutritional deficiency | 2 | 2.8 | 6 | 6.6 | 0.47 | 0 | 0 | 8 | 5.4 | 1 |
| Obesity | 18 | 25.0 | 33 | 36.3 | 0.13 | 2 | 13.3 | 49 | 33.1 | 0.15 |
| BMI (mean, SD) | 27.59 | ±5.79 | 28.47 | ±6.00 | 0.35 | 26.88 | ±3.58 | 28.21 | ±6.10 | 0.41 |
| Antiviral use | ||||||||||
| Oseltamivir | 56 | 77.8 | 33 | 36.3 | <0.001 | 8 | 53.3 | 81 | 54.7 | 1.00 |
| Zanamivir | 4 | 5.6 | 1 | 1.1 | 0.17 | 0 | 0.0 | 5 | 3.4 | 1.00 |
| SIV in 2014–2015 season | 2 | 2.9 | 6 | 6.7 | 0.47 | 6 | 46.2 | 2 | 1.4 | ≤0.001 |
| SIV in 2015–2016 season | 4 | 5.6 | 11 | 12.1 | 0.18 | – | - | - | - | - |
| Length of hospitalisation (mean, SD) | 7.5 | ±6.0 | 9.2 | ±6.0 | 0.07 | 9.1 | ±4.2 | 8.4 | ±6.2 | 0.04 |
| Transfer to the intensive care unit | 6 | 8.3 | 1 | 1.1 | 0.05 | 1 | 6.7 | 6 | 4.1 | 0.50 |
| Deaths | 4 | 5.6 | 1 | 1.1 | 0.17 | 1 | 6.7 | 4 | 2.7 | 0.39 |
BMI, body mass index; GP, general practitioner; SIV, seasonal influenza vaccination.