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Table 2 Sociodemographic characteristics and SARS-CoV-2 specific information of the CoCoS study participants (first and second round) compared to the potential participants and to the general adult Cologne population

From: Results of the Cologne Corona surveillance (CoCoS) study – a prospective population-based cohort study: incidence data and potential underestimation of new SARS-CoV-2 adult infections by health authorities

  General adult Cologne population Potential participants CoCoS round #1 Participants CoCoS round #1 Potential participants round #2 Second examination CoCoS study
Sample
 Participants (18 yrs. or older)1 913,009 100% 6000 100% 2045 34.08% 6000 100% 2192 36.53%
Gendera
 Female 470,577 51.54% 3090 51.51% 1088 53.20% 3086 51.44% 1189 54.24%
Agea
 18–34 years (%) 270,538 29,63% 1795 29.92% 518 25.33% 1662 27.70% 506 23.08%
 35–59 years old (%) 388,678 42,57% 2560 42.67% 951 46.50% 2640 44.01% 996 45.44%
 60–74 years old (%) 153,890 16,86% 1007 16.79% 418 20.44% 1095 18.25% 474 21.62%
 75 years or older (%) 99,903 10,94% 637 10.62% 158 7.73% 602 10.04% 216 9.85%
No. of household members
 Average 913,009 1.88 NA NA 1580 2.36 NA NA 1689 2.32
 1–2 438,859 77.68% NA NA 1055 66.77% NA NA 1158 68.56%
 3–4 106,314 18.82% NA NA 455 28.80% NA NA 472 27.95%
 5 or more 19,800 3.50% NA NA 70 4.43% NA NA 59 3.49%
 Missing valuesb 465 22.74% 503 22.95%
School education
 No school leaving certificate 36,520 4.00% NA NA 8 0.50% NA NA 8 0.46%
 Secondary school diploma 374,333 41.00% NA NA 400 24.99% NA NA 419 24.22%
 High school graduation 502,155 55.00% NA NA 1193 74.52% NA NA 1303 75.32%
 Missing valuesb 444 21.71% 462 21.08%
Employment status
 Student/apprenticeship 122,849 13.46% NA NA 163 9.85% NA NA 161 9.10%
 Employed 582,613 63.81% NA NA 971 58.71% NA NA 1025 57.91%
 Self-employed NA NA NA NA 179 10.82% NA NA 201 11.36%
 Retired NA NA NA NA 243 14.69% NA NA 288 16.27%
 Unemployed 45,225 4.60% NA NA 38 2.23% NA NA 40 2.26%
 Other2 NA NA NA NA 60 3.63% NA NA 60 3.40%
 Missing Valuesb 391 19.12% 422 19.25%
Primary citizenshipa
 German 727,503 79.68% 4677 77.96% 1894 92.62% 5039 84.00% 2067 94.30%
 other than German 185,506 20.32% 1322 22.04% 151 7.38% 960 16.00% 125 5.70%
Cumulative SARS-CoV-2 cases
 Start of the pandemic until March 14, 2021 32,119 3.52% NA NA 67 3.71%
[2.78, 4.64%]
NA NA NA NA
 Start of the pandemic until June 6, 2021 46,195 5.06% NA NA NA NA NA NA 90 4.61%
[3.60, 5.61%]
Vaccination rate until March 15, 2021
 Vaccinated at least once 82,718 9,06% NA NA 159 9.66% NA NA NA NA
 Vaccinated twice 39,684 4.35% NA NA 59 3.58% NA NA NA NA
 Not vaccinated 839,291 90.94% NA NA 1487 90.34% NA NA NA NA
 Missing Valuesb NA NA NA NA 399 19.51% NA NA NA NA
Vaccination rate until June 4, 2021
 Vaccinated at least once 529,248 57,97% NA NA NA NA NA NA 1396 79.82%
 Vaccinated twice 220,987 24.20% NA NA NA NA NA NA 589 33.68%
 Not vaccinated 383,761 42.03% NA NA NA NA NA NA 353 20.18%
 Missing Valuesb NA NA NA NA NA NA NA NA 443 20.21%
  1. aInformation obtained directly from the population register
  2. bWhile the percentages on the variables expressed relate to the respondents of the respective questionnaire item, the percentages on the missing values relate to the sample (N = 2045/N = 2192)