Table 1.

Association between selected variables and prevalence of positive tests (anti-SARS-CoV-2 IgG ≥15 AU/mL) among healthcare workers in a large university hospital, Milan, Italy, 27 April 2020 to 12 June 2020

Variable	Workers	Positive test
	N	N	%	P value*	OR†	95% CI†
All	4055	309	7.6
Country of origin
Italy	3869	282	7.3	<0.001	1.00	Reference
Other	186	27	14.5		1.82	1.07 to 3.06
Gender
Women	2823	207	7.3	0.30	1.00	Reference
Men	1232	102	8.3		1.13	0.85 to 1.52
Age (years)
<30	668	64	9.6	0.02	1.00	Reference
30–39	1018	78	7.7		0.74	0.51 to 1.07
40–49	858	48	5.6		0.46	0.30 to 0.72
50–59	1128	81	7.2		0.64	0.43 to 0.95
60+	383	38	9.9		0.83	0.50 to 1.36
Occupation
Physicians, including residents	1292	93	7.2	0.006	0.99	0.64 to 1.53
Nurses, midwives	1230	99	8.0		1.31	0.85 to 2.04
Healthcare assistants	320	40	12.5		1.84	1.04 to 3.25
Health technicians‡	585	35	6.0		0.84	0.50 to 1.40
Clerical workers, technicians	628	42	6.7		1.00	Reference
Frontline healthcare workers
Never	2061	149	7.2	0.42	1.00	Reference
Ever	1730	137	7.9		0.92	0.69 to 1.24
Missing	264	23	8.7
BMI
<20	684	46	6.7	0.04	0.90	0.62 to 1.32
20–24.99	2035	145	7.1		1.00	Reference
25–29.99	945	79	8.4		1.10	0.80 to 1.52
30+	314	31	9.9		1.52	0.98 to 2.35
Missing	77	8	10.4
Cigarette smoking
Never	2493	210	8.4	<0.001	1.00	Reference
Former	552	49	8.9		1.12	0.79 to 1.58
Current	842	34	4.0		0.41	0.27 to 0.61
Missing	168	16	9.5

*From χ² test. For BMI: from χ² test for trend. Missing data not included in analyses.

†From a multivariable logistic regression model including country of origin, gender, age, occupation, frontline area, BMI and smoking. Missing data not included in analyses.

‡Includes biologists, radiology and laboratory technicians, psychologists and other health technicians.

BMI, body mass index.;