Table 3.

Key SARS-CoV-2 Epidemiological Measures Assessed in the Study

Epidemiological Measure	Sample (Denominator)	Positive for Outcome (Numerator)	Estimate (95% CI), %a
Antibody positivity (seropositivity) prevalence	2641	1427	55.3 (53.3–57.3)
PCR positivity prevalence	2092b	233	11.3 (9.9–12.8)
Infection (antibody and/or PCR) positivity prevalence	2641	1571	60.6 (58.6–62.5)
Infection diagnosis ratec	1427	131	9.3 (7.9–11.0)
Antibody-negative CMWs previously PCR-diagnosed with SARS-CoV-2 infection	1214	4	0.4 (0.1–1.0)
Infection severity rated	1590e	8f	0.5 (0.2–1.0)

Abbreviations: CMWs, craft and manual workers; PCR, polymerase chain reaction; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

^aEstimates weighted by age, nationality, and center.

^bOnly 2092 persons consented to have nasopharyngeal and oropharyngeal swabs.

^cProportion of antibody-positive CMWs with a prior SARS-CoV-2 laboratory-confirmed PCR diagnosis.

^dNumber of infections ever severe or critical per World Health Organization criteria over total number of laboratory-confirmed infections (antibody and/or PCR positive).

^eThis number includes also 4 persons who were antibody negative and PCR negative at the time of the survey but had a PCR-positive result before the survey. This number also includes 15 persons who were antibody negative and PCR negative at the time of the survey but had a PCR-positive result subsequent to the survey at the time of data linking and analysis (October 7, 2020).

^fSeven participants in this study had ever had (or progressed to) a severe infection and 1 had a critical infection per World Health Organization infection severity classification [24] at the time of data linking and analysis (October 7, 2020).