Table 2 Estimated number of true infections using different definitions of N-antibody seropositivity

Total observed infections

(N-antibody or swab-positivity)

31,716

31,716

39,511

30,047

31,577

N (%) (95% CI) identified by N-antibody

24,440 77.1%

(76.6–77.5%)

24,139 76.1%

(75.6–76.6%)

32,702 82.8%

(82.4–83.1%)

20,999 69.9%

(69.4–70.4%)

23,161 73.3%

(72.9–73.8%)

N (%) (95% CI) identified by swab-positivity

25,404 80.1%

(79.7–80.5%)

25,200 79.5%

(79.0–79.9%)

25,404 64.3%

(63.8–64.8%)

25,404 84.5%

(84.1–85.0%)

25,404 80.5%

(80.0–80.9%)

N (%) (95% CI) identified by both

18,128 57.2%

(56.6–57.7%)

17,623 55.6%

(55.0–56.1%)

18,595 47.1%

(46.6–47.6%)

16,356 54.4%

(53.9–55.0%)

16,988 53.8%

(53.2–54.3%)

Estimated true infections* (95% CI)

34,249

(34,115–34,383)

34,517

(34,374–34,663)

44,676

(44,460–44,874)

32,615

(32,477-32,753)

34,634

(34,482 – 34,784)

% undetected by both methods (95% CI)

7.4%

(7.0–7.8%)

8.1%

(7.7–8.5%)

11.6%

(11.1–12.0%)

7.9%

(7.5–8.3%)

8.8%

(8.4–9.2%)

% undetected by N-antibody (95% CI)

28.6%

(28.4–28.9%)

30.1%

(29.8–30.4%)

26.8%

(26.4–27.1%)

35.6%

(35.3–35.9%)

33.1%

(32.8 – 33.4%)

% undetected by swab-positivity (95% CI)

25.8%

(25.5–26.1%)

27.0%

(26.7–27.3%)

43.1%

(42.9–43.4%)

22.1%

(21.8–22.4%)

26.7%

(26.3 – 27.0%)