Respondent characteristics (n=451)
| Age (years), mean (SD) | 49.8 (15.2) |
| Sex, female | 253 (56) |
| Marital status | |
| Single/divorced/separated | 99 (22) |
| Married/cohabiting | 332 (74) |
| Widowed | 19 (4) |
| Born in Norway (n=447) | 376 (84) |
| Norwegian mother tongue (n=448) | 375 (84) |
| Both parents born in Norway (n=450) | 350 (78) |
| Highest attained education | |
| Primary school | 41 (9) |
| Secondary school | 170 (38) |
| University | 240 (53) |
| Smoking status (n=446) | |
| Never smoker | 292 (65) |
| Ex-smoker | 128 (29) |
| Current smoker | 26 (6) |
| Body mass index (kg/m2) (n=444) | 26.8 (5.2) |
| Influenza vaccination second half of 2019 (n=449) | 140 (31) |
| No. of 21 comorbidities | |
| 0 | 228 (51) |
| 1 | 128 (28) |
| 2 or more | 95 (21) |
| Place of contraction | |
| Norway, known contact | 191 (42) |
| Norway, unknown contact | 142 (32) |
| Travel abroad | 115 (16) |
Number (%), unless specified otherwise.