Table 3

Risk factor analysis for SARS-CoV-2 seropositivity among all participants (n=3100; full case analysis) in the PICO-study, first round of inclusion

			% SARS-CoV-2 seropositive		Univariable model*				Multivariable model
		n_total	n	%	OR	95% CI		P value	Adjusted OR	95% CI		P value
Age group								0.016				0.105
	2–12	457	4	0.9	Ref.				Ref.
	13–17	129	1	0.8	0.88	0.10	7.91		0.87	0.10	7.91
	18–24	226	12	5.3	6.47	2.05	20.43		4.52	1.40	14.58
	25–39	696	24	3.5	4.17	1.43	12.14		3.10	1.05	9.14
	40–49	429	11	2.6	3.05	0.96	9.68		2.48	0.77	7.98
	50–59	485	8	1.7	1.94	0.58	6.49		1.49	0.44	5.07
	60–69	377	7	1.9	2.16	0.63	7.44		1.71	0.49	5.98
	70–90	301	7	2.3	2.64	0.76	9.14		2.46	0.70	8.60
Sex								0.81				0.57
	Men	1368	32	2.3	Ref.				Ref.
	Women	1732	42	2.4	1.06	0.66	1.71		1.15	0.71	1.88
Region†								0.64				0.36
	North	537	7	1.3	Ref.				Ref.
	Mid-West	411	11	2.7	2.14	0.80	5.72		2.27	0.86	5.98
	Mid-East	494	14	2.8	2.27	0.89	5.80		2.00	0.79	5.04
	South-West	451	11	2.4	1.83	0.69	4.86		1.80	0.69	4.74
	South-East	652	17	2.6	2.04	0.82	5.07		2.08	0.85	5.12
	LVC	555	14	2.5	1.80	0.71	4.61		1.09	0.40	2.94
Orthodox-Reformed Protestant								0.001				0.0007
	No	2972	65	2.2	Ref.				Ref.
	Yes	128	9	7.0	4.04	1.72	9.48		4.50	1.89	10.74
Had been in contact with a COVID-19 confirmed case								<0.0001				<0.0001
	No	2074	33	1.6	Ref.				Ref.
	Yes	192	16	8.3	4.65	2.44	8.87		4.97	2.58	9.56
	Don’t know	834	25	3.0	1.75	1.03	2.99		1.88	1.10	3.22
Took immunosuppressants, last month								0.006				0.001
	No	3039	69	2.3	Ref.				Ref.
	Yes	61	5	8.2	3.94	1.50	10.39		5.05	1.89	13.48
Took antibiotics/antiviral medication, last month								0.01
	No	2901	64	2.2	Ref.
	Yes	199	10	5.0	2.43	1.21	4.89

*Variables that were not associated with SARS-CoV-2 seropositivity in univariable analyses (ie, p≥0.10)—or that were not controlled for—included: ethnic background, (maternal) educational level, household size, (parent with a) contact profession, healthcare worker, number of persons contacted yesterday, working from home (normally and in the last week (during lockdown)), comorbidities (combining chronic lung disease, diabetes, history of malignancy, immunodeficiency, cardio-vascular disease, kidney disease), and use of blood pressure medication, immunosuppressants, statins and antivirals/antibiotics in the last month.
†Region North comprised provinces Groningen, Friesland, Drenthe and Overijssel, region Mid-West provinces Noord-Holland and Flevoland, region Mid-West provinces Utrecht and Gelderland, region South-West provinces Zuid-Holland and Zeeland, and region South-East provinces Noord-Brabant and Limburg.
CI, Confidence interval; LVC, Low vaccination coverage municipalities; OR, Odd ratio; Ref., Reference category.