Table 2.

Characteristics of the three risk groups; data are presented as n (%)

Group†	Exercised proper use of PPE	Diagnosed with COVID-19	Symptomatic at diagnosis	Positive serology* with prior diagnosis of COVID-19	Positive serology* with no prior diagnosis of COVID-19	Negative serology with prior diagnosis of COVID-19
Group 1 N = 392	366 (93.4%)	83 (21.2%)	52 (62.6%)	69 (83.1%)	15 (5.3%)	14 (16.8%)
Group 2 N = 463	377 (81.4%)	93 (20.1%)	75 (80.6%)	77 (82.7%)	10 (3.5%)	16 (17.2%)
Group 3 N = 221	NA	115	64 (55.6%)	95 (82.6%)	22 (20.7%)	20 (17.3%)

NA: not applicable

^†There was an overlap between the groups in 27 subjects who took care of COVID-19 patients and were in contact with infected employees.

^⁎Serology included both IgG and IgM antibodies.