Table 1.

Baseline Demographics

Characteristic	Placebo	Hydroxychloroquine once weekly	Hydroxychloroquine twice weekly
Number Randomized	494	494	495
Age in years, median (IQR)	40 (34, 48)	42 (35, 49)	41 (35, 49)
Weight in kg, median (IQR)	80 (68,95)	79 (67,93)	82 (68, 95)
Female* –no. (%)	241 (48.8%)	261 (52.8%)	258 (52.1%)
Ethnicity (all that apply) –no. (%)
White or Caucasian	419 (84.8%)	431 (87.2%)	421 (85.1%)
Black or African	10 (2.0%)	5 (1.0%)	5 (1.0%)
Asian	29 (5.9%)	23 (4.7%)	23 (4.6%)
Native Hawaiian or Pacific Islander	1 (0.2%)	0 (0.0%)	1 (0.2%)
Hispanic or Latino	18 (3.6%)	18 (3.6%)	22 (4.4%)
Native American or Alaska Native	8 (1.6%)	4 (0.8%)	7 (1.4%)
Middle Eastern	4 (0.8%)	6 (1.2%)	5 (1.0%)
South Asian	12 (2.4%)	17 (3.4%)	18 (3.6%)
Other	4 (0.8%)	3 (0.6%)	1 (0.2%)
Current Smoker –no. (%)	13 (2.6%)	17 (3.4%)	21 (4.2%)
Chronic Health Conditions –no. (%)
High blood pressure	60 (12.1%)	79 (16.0%)	66 (13.3%)
Asthma	59 (11.9%)	46 (9.3%)	45 (9.1%)
None	336 (68.0%)	311 (63.0%)	335 (67.7%)
Covid-19 risk factors at screening
Interacted with Covid19 patients when NOT wearing a mask OR face shield? –no. (%)
Yes	62 (12.6%)	69 (14.1%)	85 (17.2%)
No	432 (87.4%)	422 (85.9%)	409 (82.8%)
Perform aerosol-generating procedures? –no. (%)	410 (83.0%)	378 (77.0%)	377 (76.3%)
Aerosol-generating procedures performed per week –mean (SD)	10 (31.4)	9 (12.2)	9 (12.5)
Setting of occupational exposure –no. (%)
Emergency Department	190 (38.5%)	210 (42.5%)	207 (40.8%)
Intensive Care Unit	85 (17.2%)	82 (16.6%)	102 (20.6%)
Operating Room	75 (15.2%)	61 (12.3%)	42 (8.5%)
COVID-19 ward	56 (11.3%)	51 (10.3%)	47 (9.5%)
Ambulance	45 (9.1%)	40 (8.1%)	33 (6.7%)
Congregate Care Setting	20 (4.0%)	19 (3.8%)	27 (5.5%)

^*No pregnant women enrolled, 30 women reported breastfeeding at baseline.