SARS-CoV-2 IgG seropositivity by study group
| Study group | Total | IgG positive |
| Group 1* | 99 | 72 (72.7) |
| Group 2† | 106 | 2 (1.9) |
| Group 3‡ | 91 | 1 (1.1) |
| Group 4§ | 100 | 1 (1.0) |
| Group 5¶ | 107 | 2 (1.9) |
| Total | 503 | 78 (15.5) |
Data are presented as n (%) or total in first column.
*RT-PCR-confirmed COVID-19 infection (>1 month postpositive RT-PCR).
†Close contacts of persons with COVID-19 infection and who subsequently developed symptoms (virus not detected by RT-PCR on oropharyngeal/nasopharyngeal swab).
‡Close contacts of COVID-19 cases and who remained asymptomatic.
§HCWs working in areas determined as high-risk clinical areas.
¶HCWs working in areas determined as low-risk clinical areas.
HCW, healthcare worker; RT-PCR, real-time PCR.