Table 1. Characteristics of the sample, stratified by canton and age group, Ticino and Zurich, Switzerland, March 2022 (n = 1,894).
| Study site | Ticino | Zurich | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Age category in years | All | 16–29 | 30–44 | 45–64 | ≥ 65 | All | 16–29 | 30–44 | 45–64 | ≥ 65 | |
| Sample size | 850 | 176 | 208 | 262 | 204 | 1,044 | 183 | 260 | 326 | 275 | |
| Median age in years | 48 | 23 | 38 | 54 | 72 | 50 | 24 | 37 | 55 | 72 | |
| IQR | 32–64 | 19–27 | 34–42 | 49–58 | 68–77 | 34–65 | 21–27 | 33–41 | 51–59 | 68–77 | |
| Age group in years | |||||||||||
| 16–29 | Number | 176 | 176 | 0 | 0 | 0 | 183 | 183 | 0 | 0 | 0 |
| Percentage | 20.7 | 100.0 | 0.0 | 0.0 | 0.0 | 17.5 | 100.0 | 0.0 | 0.0 | 0.0 | |
| 30–44 | Number | 208 | 0 | 208 | 0 | 0 | 260 | 0 | 260 | 0 | 0 |
| Percentage | 24.5 | 0.0 | 100.0 | 0.0 | 0.0 | 24.9 | 0.0 | 100.0 | 0.0 | 0.0 | |
| 45–64 | Number | 262 | 0 | 0 | 262 | 0 | 326 | 0 | 0 | 326 | 0 |
| Percentage | 30.8 | 0.0 | 0.0 | 100.0 | 0.0 | 31.2 | 0.0 | 0.0 | 100.0 | 0.0 | |
| ≥ 65 | Number | 204 | 0 | 0 | 0 | 204 | 275 | 0 | 0 | 0 | 275 |
| Percentage | 24.0 | 0.0 | 0.0 | 0.0 | 100.0 | 26.3 | 0.0 | 0.0 | 0.0 | 100.0 | |
| Sexa | |||||||||||
| Female | Number | 484 | 103 | 125 | 152 | 104 | 567 | 106 | 157 | 169 | 135 |
| Percentage | 56.9 | 58.5 | 60.1 | 58.0 | 51.0 | 54.3 | 57.9 | 60.4 | 51.8 | 49.1 | |
| Educational level | |||||||||||
| Primary | Number | 89 | 39 | 6 | 10 | 34 | 71 | 31 | 7 | 10 | 23 |
| Percentage | 10.5 | 22.2 | 2.9 | 3.8 | 16.7 | 6.8 | 16.9 | 2.7 | 3.1 | 8.4 | |
| Secondary | Number | 475 | 90 | 82 | 180 | 123 | 428 | 79 | 68 | 127 | 154 |
| Percentage | 55.9 | 51.1 | 39.4 | 68.7 | 60.3 | 41.0 | 43.2 | 26.2 | 39.0 | 56.0 | |
| Tertiary | Number | 278 | 46 | 120 | 70 | 42 | 537 | 73 | 181 | 187 | 96 |
| Percentage | 32.7 | 26.1 | 57.7 | 26.7 | 20.6 | 51.4 | 39.9 | 69.6 | 57.4 | 34.9 | |
| Missing | Number | 8 | 1 | 0 | 2 | 5 | 8 | 0 | 4 | 2 | 2 |
| Percentage | 0.9 | 0.6 | 0.0 | 0.8 | 2.5 | 0.8 | 0.0 | 1.5 | 0.6 | 0.7 | |
| Household income (CHF/month) | |||||||||||
| 0–6,000 | Number | 371 | 79 | 64 | 107 | 121 | 353 | 97 | 50 | 62 | 144 |
| Percentage | 43.6 | 44.9 | 30.8 | 40.8 | 59.3 | 33.8 | 53.0 | 19.2 | 19.0 | 52.4 | |
| 6,000–12,000 | Number | 306 | 55 | 100 | 96 | 55 | 392 | 43 | 108 | 143 | 98 |
| Percentage | 36.0 | 31.2 | 48.1 | 36.6 | 27.0 | 37.5 | 23.5 | 41.5 | 43.9 | 35.6 | |
| 12,000–18,000 | Number | 59 | 13 | 20 | 24 | 2 | 173 | 30 | 60 | 70 | 13 |
| Percentage | 6.9 | 7.4 | 9.6 | 9.2 | 1.0 | 16.6 | 16.4 | 23.1 | 21.5 | 4.7 | |
| ≥ 18,000 | Number | 45 | 7 | 15 | 16 | 7 | 75 | 7 | 30 | 36 | 2 |
| Percentage | 5.3 | 4.0 | 7.2 | 6.1 | 3.4 | 7.2 | 3.8 | 11.5 | 11.0 | 0.7 | |
| Missing | Number | 69 | 22 | 9 | 19 | 19 | 51 | 6 | 12 | 15 | 18 |
| Percentage | 8.1 | 12.5 | 4.3 | 7.3 | 9.3 | 4.9 | 3.3 | 4.6 | 4.6 | 6.5 | |
| Employment status | |||||||||||
| Working | Number | 529 | 126 | 183 | 208 | 12 | 731 | 177 | 237 | 292 | 25 |
| Percentage | 62.2 | 71.6 | 88 | 79.4 | 5.9 | 70 | 96.7 | 91.2 | 89.6 | 9.1 | |
| Missing | Number | 5 | 1 | 1 | 1 | 2 | 8 | 0 | 4 | 1 | 3 |
| Percentage | 0.6 | 0.6 | 0.5 | 0.4 | 1.0 | 0.8 | 0.0 | 1.5 | 0.3 | 1.1 | |
| Swiss citizenship | |||||||||||
| Swiss citizen | Number | 677 | 161 | 138 | 212 | 166 | 880 | 157 | 180 | 284 | 259 |
| Percentage | 79.6 | 91.5 | 66.3 | 80.9 | 81.4 | 84.3 | 85.8 | 69.2 | 87.1 | 94.2 | |
| Missing | Number | 3 | 0 | 0 | 2 | 1 | 6 | 0 | 3 | 1 | 2 |
| Percentage | 0.4 | 0.0 | 0.0 | 0.8 | 0.5 | 0.6 | 0.0 | 1.2 | 0.3 | 0.7 | |
| Lifestyle and conditions | |||||||||||
| Smoking | Number | 178 | 56 | 47 | 52 | 23 | 192 | 37 | 54 | 70 | 31 |
| Percentage | 20.9 | 31.8 | 22.6 | 19.8 | 11.3 | 18.4 | 20.2 | 20.8 | 21.5 | 11.3 | |
| Missing | Number | 3 | 0 | 0 | 1 | 2 | 5 | 0 | 1 | 1 | 3 |
| Percentage | 0.4 | 0.0 | 0.0 | 0.4 | 1.0 | 0.5 | 0.0 | 0.4 | 0.3 | 1.1 | |
| Obese (BMI ≥ 30) | Number | 102 | 8 | 24 | 37 | 33 | 132 | 11 | 27 | 55 | 39 |
| Percentage | 12 | 4.5 | 11.5 | 14.1 | 16.2 | 12.6 | 6 | 10.4 | 16.9 | 14.2 | |
| Missing | Number | 1 | 0 | 0 | 1 | 0 | 2 | 0 | 1 | 1 | 0 |
| Percentage | 0.1 | 0.0 | 0.0 | 0.4 | 0.0 | 0.2 | 0.0 | 0.4 | 0.3 | 0.0 | |
| ≥ 1 chronic condition | Number | 188 | 14 | 16 | 56 | 102 | 283 | 13 | 30 | 81 | 159 |
| Percentage | 22.1 | 8 | 7.7 | 21.4 | 50 | 27.1 | 7.1 | 11.5 | 24.8 | 57.8 | |
| Missing | Number | 1 | 0 | 0 | 0 | 1 | 2 | 0 | 1 | 1 | 0 |
| Percentage | 0.1 | 0.0 | 0.0 | 0.0 | 0.5 | 0.2 | 0.0 | 0.4 | 0.3 | 0.0 | |
| Previous SARS-CoV-2 infection | |||||||||||
| Positive test (ever) | Number | 356 | 91 | 112 | 111 | 42 | 339 | 76 | 107 | 100 | 56 |
| Percentage | 41.9 | 51.7 | 53.8 | 42.4 | 20.6 | 32.5 | 41.5 | 41.2 | 30.7 | 20.4 | |
| Missing | Number | 0 | 0 | 0 | 0 | 0 | 3 | 0 | 1 | 1 | 1 |
| Percentage | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.3 | 0.0 | 0.4 | 0.3 | 0.4 | |
| Infected recently (NuC antibody positive) | Number | 230 | 64 | 71 | 61 | 34 | 238 | 52 | 73 | 79 | 34 |
| Percentage | 27.1 | 36.4 | 34.1 | 23.3 | 16.7 | 22.8 | 28.4 | 28.1 | 24.2 | 12.4 | |
| Infected recently (NuC antibody positive or positive test 2022) | Number | 318 | 86 | 102 | 92 | 38 | 318 | 71 | 99 | 102 | 46 |
| Percentage | 37.4 | 48.9 | 49 | 35.1 | 18.6 | 30.5 | 38.8 | 38.1 | 31.3 | 16.7 | |
| Past severe infections 2020–2022b | Number | 13 | 0 | 0 | 4 | 9 | 6 | 0 | 0 | 1 | 5 |
| Percentage | 1.5 | 0.0 | 0.0 | 1.5 | 4.4 | 0.6 | 0.0 | 0.0 | 0.3 | 1.8 | |
| Missing | Number | 1 | 0 | 0 | 1 | 0 | 2 | 0 | 0 | 1 | 1 |
| Percentage | 0.1 | 0.0 | 0.0 | 0.4 | 0.0 | 0.2 | 0.0 | 0.0 | 0.3 | 0.4 | |
| Vaccination against SARS-CoV-2 | |||||||||||
| Vaccinated (≥ 1 dose) | Number | 765 | 158 | 184 | 237 | 186 | 972 | 169 | 238 | 298 | 267 |
| Percentage | 90 | 89.8 | 88.5 | 90.5 | 91.2 | 93.1 | 92.3 | 91.5 | 91.4 | 97.1 | |
| Missing | Number | 6 | 1 | 0 | 3 | 2 | 4 | 1 | 2 | 1 | 0 |
| Percentage | 0.7 | 0.6 | 0.0 | 1.1 | 1.0 | 0.4 | 0.5 | 0.8 | 0.3 | 0.0 | |
| Booster dose | Number | 494 | 74 | 114 | 164 | 142 | 758 | 122 | 178 | 240 | 218 |
| Percentage | 58.1 | 42 | 54.8 | 62.6 | 69.6 | 72.6 | 66.7 | 68.5 | 73.6 | 79.3 | |
| Missing | Number | 100 | 19 | 24 | 27 | 30 | 79 | 14 | 23 | 30 | 12 |
| Percentage | 11.8 | 10.8 | 11.5 | 10.3 | 14.7 | 7.6 | 7.7 | 8.8 | 9.2 | 4.4 | |
BMI: body mass index; CHF: Swiss francs; ICU: intensive care unit; IQR: interquartile range; NuC: nucleocapsid; SARS-CoV-2: severe acute respiratory coronavirus 2.
a Sex was collected as a binary variable (male; female).
b Severe infections were defined as those requiring a hospital admission (among those three ICU admissions in participants from Ticino and none in Zurich).