| Gender (men vs women) | 1.41 (1.38 to 1.43) |
| Age | |
| 40–49 | 0.1 (0.11 to 0.13) |
| 50–59 | 0.3 (0.35 to 0.38) |
| 60–69 | 1.00 |
| 70–79 | 2.1 (2.06 to 2.18) |
| 80–89 | 3.7 (3.66 to 3.88) |
| ≥90 | 6.7 (6.49 to 7.00) |
| Season (December to March vs April to November) | 1.3 (1.33 to 1.40) |
| Unexpected influenza strain | 1.1 (1.13 to 1.25) |
| Myocardial infarction | 1.2 (1.23 to 1.30) |
| Congestive heart disease | 2.1 (2.12 to 2.22) |
| Peripheral vascular disease | 1.3 (1.33 to 1.40) |
| Cerebrovascular disease | 1.3 (1.34 to 1.40) |
| Dementia | 2.3 (2.22 to 2.44) |
| Rheumatic disease | 1.1 (1.09 to 1.18) |
| Peptic ulcer disease | 1.1 (1.07 to 1.14) |
| Mild liver disease | 2.1 (1.86 to 2.42) |
| Diabetes | 1.2 (1.25 to 1.32) |
| Diabetes with chronic disorders | 1.0 (0.90 to 1.19) |
| Hemiplegia or paraplegia | 1.4 (1.35 to 1.61) |
| Renal disease | 1.7 (1.71 to 1.87) |
| Any malignancy | 1.4 (1.39 to 1.45) |
| Moderate or severe liver disease | 2.9 (2.49 to 3.57) |
| Metastatic solid tumour | 3.9 (3.70 to 4.21) |