Table 2. SARS-CoV-2 IgG seropositivity in selected demographic groups of the final study sample, Norway, winter 2020/21 (n = 234).

Variables	Positive tests	Crude seroprevalence			Weighted seroprevalence
	n	%	95% CI		%	95% CI
Data from Statistics Norway
IgG seropositive cases	234	0.8		0.7–1.0	0.9	0.7–1.0
Age groups
16–19	16	1.8		1.1–3.0	1.9	0.9–2.9
20–44	100	1.0		0.8–1.2	1.0	0.8–1.2
45–66	86	0.8		0.6–1.0	0.7	0.6–0.9
67–79	29	0.6		0.4–0.9	0.5	0.3–0.7
≥ 80	3	0.4		0.1–1.2	0.4	0.0–0.9
Sex
Women	133	0.8		0.7–1.0	0.8	0.6–1.0
Men	101	0.9		0.7–1.0	0.9	0.7–1.1
Place of birth
Nordic countries	184	0.8		0.7–0.9	0.7	0.6–0.9
Outside Nordic countries	50	1.4		1.0–1.8	1.4	1.0–1.9
Counties
Troms and Finnmark	12	0.7		0.4–1.3	0.7	0.2–1.1
Nordland	6	0.5		0.3–1.1	0.4	0.0–0.9
Trøndelag	8	0.4		0.2–0.7	0.4	0.0–0.8
Møre and Romsdal	1	0.1		0.0–0.6	0.0	0.0–0.1
Vestland	39	1.2		0.9–1.6	1.4	0.9–1.8
Rogaland	15	0.7		0.4–1.2	0.7	0.3–1.2
Agder	9	0.7		0.3–1.3	0.7	0.1–1.2
Vestfold and Telemark	6	0.3		0.1–0.6	0.2	0.0–0.4
Viken	67	1.0		0.8–1.3	1.0	0.7–1.3
Oslo	60	1.6		1.2–2.0	1.7	1.2–2.2
Innlandet	10	0.6		0.3–1.0	0.6	0.2–1.1
Data from questionnaire
Education level
Primary school/junior high school	17	0.8		0.5–1.3	NA
High school	54	0.8		0.6–1.0	NA
Vocational school	22	0.6		0.4–0.9	NA
University or college	127	0.9		0.8–1.1	NA
Healthcare worker
Yes	42	1.1		0.8–1.5	NA
No	178	0.8		0.7–0.9	NA
Number of people living in household
1	37	0.8		0.6–1.2	NA
2–4	161	0.8		0.7–1.0	NA
≥ 5	22	1.0		0.6–1.4	NA

CI: 95% confidence interval; NA: not applicable; SARS-CoV-2: severe acute respiratory syndrome coronavirus 2.