Table 2.

Serological Status and Seroprevalence Among Danish Blood Donors by Age

Serological Status and Seroprevalence	Weeks 41 to 44, 2020	Weeks 5 to 8, 2021
SARS-CoV-2 serological status
Seronegative, age, y, n (%)
17–35	8217 (37)	7066 (37)
36–50	6971 (31)	5846 (31)
51–60	4651 (21)	3994 (21)
61–69	2292 (10)	1983 (10)
Total	22131 (100)	18889 (100)
Seropositive, age, y, n (%)
17–35	255 (46)	735 (49)
36–50	161 (29)	422 (28)
51–60	111 (20)	257 (17)
61–69	32 (6)	95 (6)
Total	559 (100)	1509 (100)
Donor seroprevalence
Unadjusted seroprevalence, age, y, %
17–35	3.01	9.42
36–50	2.26	6.73
51–60	2.33	6.05
61–69	1.38	4.57
Total	2.46	7.40
Adjusted seroprevalence, age, y, % (95% CI)a
17–35	2.65 (1.70–3.16)	9.31 (8.27–10.15)
36–50	1.87 (.91–2.36)	6.52 (5.47–7.29)
51–60	1.94 (.96–2.51)	5.80 (4.70–6.66)
61–69	0.95 (.00–1.58)	4.27 (3.05–5.32)
Total	2.08 (1.16–2.47)	7.21 (6.30–7.78)

Serological status and seroprevalence among Danish blood donors stratified by age for week 41 to 44, 2020 and week 5 to 8, 2021. The exact numbers stratified by region and age were used in the estimation of the number of SARS-CoV-2 seropositives. However, due to low numbers of seropositives in specific age strata for some regions, only total numbers and seroprevalences per age strata are presented.

Abbreviations: CI, confidence interval; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

Seroprevalence adjusted for assay sensitivity and specificity.