Table 3.

Prevalence of antibodies to SARS-CoV-2 among staff participants and association with demographic and employment characteristics.

	% Antibody positive (N/Total)	Adjusted OR (95% CI)
County
San Mateo County	3.4 (7/207)	Ref
Santa Clara County	20.0 (17/85)	5.5 (2.0–15.0)***
Gender
Men	10.9 (18/165)	Ref
Transgender/gender non-conforming	0 (0/1)	0 (NA)
Women	4.8 (6/126)	0.3 (0.1–0.8)*
Age
18–29	10.0 (4/40)	Ref
30–49	10.0 (14/140)	0.6 (0.2–2.2)
50+	1.4 (1/70)	0.1 (0–1.2)
Unknown	11.9 (5/42)
Race/ethnicity
Other/unknown	14.8 (8/54)	Ref
Asian	2.6 (1/38)	0.3 (0–2.8)
Black	18.2 (2/11)	1.7 (0.2–14.1)
Hispanic/Latinx	8.5 (8/94)	0.8 (0.2, 3.6)
White	5.3 (5/95)	0.5 (0.1–2.5)
Health care worker
Yes	4.8 (4/83)	Ref
No	8.2 (15/183)	0.9 (0.2, 3.4)
Prefer not to answer	19.2 (5/26)	5.3 (0–1167.1)
Contact with incarcerated individuals
No	4.9 (2/41)	Ref
Yes	7.7 (17/222)	0.9 (0.2–4.6)
Prefer not to answer	17.2 (5/29)	0.1 (0–40.6)
Flu-like illness since Feb 2020
Yes	8.8 (5/57)
No	6.8 (14/205)
Prefer not to answer	16.7 (5/30)
Perceived likelihood of past infection
Very unlikely/unlikely	2.0 (2/102)
Possible	4.6 (5/108)
Likely/very likely	10.0 (4/40)
Prefer not to answer	17.2 (5/29)
I tested positive for COVID-19	61.5 (8/13)
Total	8.2 (24/292)

Participants already vaccinated at the time of enrollment were excluded. OR, odds ratio; CI, confidence interval.

*p <0.05.

***p <0.001.