Table 2. Characteristics of prevalent cases and associated risks of having a positive serological test at baseline in healthcare workers of the two largest COVID-19 referral hospitals in Mexico City, October 2020-June 2021.

		n	(%) a	OR	95% CI	aOR	95% CI
Sex	Male	76/262	(29)			Reference
	Female	158/620	(25)	0.84	0.61–1.16	0.86	0.58–1.29
Age	N/A	N/A		1.00	0.98–1.01	1.00	0.98–1.02
Municipality	Tlalpan	65/283	(23)			Reference
	Coyoacán	22/108	(20)	0.86	0.50–1.48	0.93	0.52–1.66
	Xochimilco	26/71	(37)	1.94	1.11–3.38	2.03	1.09–3.79
	Iztapalapa	11/63	(17)	0.71	0.35–1.44	0.69	0.32–1.51
	Other b	61/223	(27)	1.26	0.84–1.89	1.31	0.85–2.02
Institution	INER	115/548	(21)			Reference
	INCMNSZ	120/335	(36)	2.10	1.55–2.85	2.24	1.54–3.25
Occupation	Physician	47/212	(22)			Reference
	Nurse	76/244	(31)	1.59	1.04–2.42	1.02	0.57–1.81
	Lab Technician	16/38	(42)	2.55	1.24–5.25	4.38	1.75–10.93
	Administrative	44/195	(23)	1.02	0.64–1.63	1.18	0.64–2.17
	Other	50/189	(26)	1.26	0.80–2.00	1.40	0.79–2.50
Contact with any person with COVID-19		129/480	(27)	1.04	0.77–1.40	0.78	0.52–1.19
Handling of biological specimens		97/326	(30)	1.29	0.95–1.75	1.09	0.67–1.77
Contact with COVID-19 patients		113/367	(31)	1.44	1.07–1.95	1.61	0.99–2.61
Use of PPE		208/812	(26)	0.57	0.34–0.95	0.60	0.32–1.13
Use of face mask		231/875	(26)	0.36	0.07–1.79	0.44	0.05–3.91
Use of public transport		121/426	(28)	1.20	0.89–1.62	1.27	0.87–1.85

aOR, adjusted odds ratio; OR, crude odds ratio; CI, confidence interval; INCMNSZ, National Institute of Medical Sciences and Nutrition; INER, National Institute of Respiratory Diseases; N/A, not applicable; PPE, Personal Protection Equipment.

^a Row percentages are shown.

^b Includes the remaining municipalities in Mexico City and municipalities in other states. Only the variables shown in the table were included in the multivariable model.