Table 4.

SARS-CoV-2 Seropositivity in Retired Blood Donors Aged 70 Years or Older and Active Blood Donors Aged 17–69 Years

	Region
	Capital	Zealand	Central Denmark	Total
Tested, ≥70 y, n
Nonreactive, n	439	452	288	1179
Reactive, n	10	9	<5	22
Total, n	449	461	291	1201
≥70 years, seroprevalence
Unadjusted, %	2.2 (1.1–4.1)	2.0 (0.9–3.7)	1.0 (0.2–3.0)	1.8 (1.2–2.8)
Adjusted, %	2.2 (0.6–4.1)	1.9 (0.4–3.7)	0.7 (−0.4–3.0)	1.4 (0.3–2.5)
Citizens, ≥70 y, n	231 731	139 827	184 324	555 882
Expected seropositives, n	5098 (1390–9501)	2656 (559–5174)	1290 (0–5529)	7782 (1668–13 897)
Confirmed cases, n	1194	394	243	1831
Ratio of confirmed cases to expected seropositives, %	23.4 (12.6–85.9)	14.8 (7.6–70.5)	18.8 (4.4–100)	23.5 (13.2–100)
Confirmed deaths, n	311	107	60	478
IFR, %	6.1 (3.3–22.4)	4.0 (2.1–19.1)	4.7 (1.1–100)	6.1 (3.4–28.6)
Tested, 17–69 y, n
Nonreactive, n	479	243	355	1077
Reactive, n	21	7	5	33
Total, n	500	250	360	1110
17–69 y, seroprevalence
Unadjusted, %	4.2 (2.6–6.3)	2.8 (1.1–5.7)	1.4 (0.5–3.2)	3.0 (2.1–4.1)
Adjusted, %	3.9 (2.1–6.0)	2.5 (0.6–5.3)	1.1 (−0.3–2.8)	2.5 (1.3–3.8)
Citizens, 17–69 y, n	1 268 536	544 560	887 939	2 701 035
Expected seropositives, n	49 472 (26 639–76 112)	13 614 (3267–28 861)	9767 (0–24 862)	67 525 (35 113–102 639)
Confirmed cases, n	5575	1543	1320	8438
Ratio of confirmed cases to expected seropositives, %	11.3 (7.3–20.9)	11.3 (5.3–47.2)	13.5 (5.3–100)	12.5 (8.2–24.0)
Confirmed deaths, n	45	17	9	71
IFR, %	0.09 (0.06 –0.17)	0.12 (0.06–0.52)	0.09 (0.04–100)	0.11 (0.07–0.2)

Abbreviations: IFR, infection fatality rate; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.