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Table 1 Number and rate per 100 person-years at risk of SARS-CoV-2 re-infections among Ku-gaa-gii pimitizi-win participants having evidence of incident infection (n = 381), by method of identification and observation period

From: Enhancing detection of SARS-CoV-2 re-infections using longitudinal sero-monitoring: demonstration of a methodology in a cohort of people experiencing homelessness in Toronto, Canada

 

Test-only method

Longitudinal serology

Comprehensive method

Period of Interest

N

Rate/100 YAR (95% CI*)

N Proa

N Pob

N Indc

N

total

Rate/100 YAR (95% CI*)

N

Rate/100 YAR (95% CI*)

March 2020 to final interview (n = 381)

37

8.71 (6.2–11.9)

NA

NA

NA

NA

NA

135

31.78 (26.8–37.5)

Baseline interview to final interview (n = 381)

31

8.98 (6.2–12.6)

21

40

37

98

28.37 (23.2–34.4)

129

37.35 (31.3–44.2)

Specific periods:

         

 March 2020 to baseline Interview (n = 202)

6

5.74 (2.3–11.9)

NA

NA

NA

NA

NA

6

5.74 (2.3–11.9)

 Baseline interview to 3-mth interview (n = 221)

0

0 (0–0)

0

3

1

4

9.33 (3.0-22.5)

4

9.33 (3.0-22.5)

 Most recent interview (baseline or 3mth) to 6-month interview (n = 318)

12

21.47 (11.6–36.5)

8

19

6

33

59.05 (41.3–82.0)

45

80.52 (59.4-106.8)

 Most recent interview (baseline, 3- or 6-mth) to 9-month interview (n = 381)

12

17.86 (9.7–30.4)

7

13

17

37

55.06 (39.3–75.1)

49

72.92 (54.5–95.6)

 Most recent interview (baseline, 3-, 6-, or 9-mth) to 12-month interview (n = 381)

7

9.34 (4.1–18.5)

6

5

13

24

32.02 (21.0-46.9)

31

41.36 (28.6–58.0)

  1. CI = Confidence Interval; YAR = Years at risk
  2. *95% confidence interval calculated using Poisson regression
  3. aPro=Probable re-infection = Serology-identified re-infections with supporting anti-R or anti-S evidence unexplained by recent vaccination
  4. bPo=Possible re-infection = Serology-identified re-infections with stable or supporting anti-R or anti-S evidence with recent vaccination
  5. cInd=Indeterminate re-infection = Serology-identified re-infections without supporting anti-R or anti-S evidence