Table 1.
Characteristics of a cohort of patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), rates of reinfection, and association with reinfection
| Total infected (%) | Number reinfected | Cumulative incidence of reinfection at 270 days, % (95%CI) | Unadjusted hazard ratio (95%CI) | Adjusted hazard ratio (95%CI) | 120-Day sensitivity analysis adjusted hazard ratio (95%CI)c | |
|---|---|---|---|---|---|---|
| Total | 75 149 | 315 | 0.8 (0.7–1.0) | N/A | N/A | N/A |
| Sex | ||||||
| Other/unknown | 13 (0.0%) | 0 | N/A | N/A | N/A | N/A |
| Female | 39 736 (52.9%) | 194 | 1.0 (0.8–1.2) | 1.45 (1.15– 1.82) | 1.44 (1.14–1.81) | 1.60 (1.21–2.12) |
| Male | 35 400 (47.1%) | 121 | 0.7 (0.5–0.9) | 1.0 (ref) | 1.0 (ref) | 1.0 (ref) |
| Age at infection, years | ||||||
| 0–17 | 6078 (8.1%) | 9 | 0.2 (0.1–0.4) | 1.0 (ref) | 1.0 (ref) | 1.0 (ref) |
| 18–39 | 31 697 (42.2%) | 148 | 0.9 (0.7–1.1) | 2.60 (1.32– 5.09) | 2.71 (1.38–5.31) | 4.19 (1.54–11.36) |
| 40–59 | 26 365 (35.1%) | 106 | 0.8 (0.6–1.0) | 2.15 (1.09– 4.24) | 2.22 (1.12–4.41) | 2.74 (0.99–7.54) |
| 60+ | 11 009 (14.6%) | 52 | 0.9 (0.5–1.2) | 2.49 (1.23– 5.06) | 2.52 (1.23–5.17) | 3.41 (1.20–9.74) |
| Race/ethnicity | ||||||
| Asian/Pacific Islander | 4242 (5.6%) | 11 | 0.5 (0.2–0.9) | 0.66 (0.34– 1.30) | 0.68 (0.35–1.33) | 0.69 (0.29–1.61) |
| Black | 4185 (5.6%) | 19 | 0.9 (0.3–2.6) | 1.31 (0.76– 2.27) | 1.25 (0.72–2.17) | 1.30 (0.65–2.62) |
| Hispanic | 49 648 (66.1%) | 227 | 0.9 (0.7–1.1) | 1.37 (0.97– 1.92) | 1.40 (0.99–1.97) | 1.59 (1.03–2.48) |
| Other/unknown | 4820 (6.4%) | 19 | 0.7 (0.2–1.2) | 1.22 (0.70– 2.11) | 1.30 (0.75–2.27) | 1.53 (0.78–3.00) |
| White | 12 254 (16.3%) | 39 | 0.7 (0.4–1.1) | 1.0 (ref) | 1.0 (ref) | 1.0 (ref) |
| Immunocompromisedb | ||||||
| Not immunocompromised | 74 196 (98.7%) | 305 | 0.8 (0.7–1.0) | 1.0 (ref) | 1.0 (ref) | 1.0 (ref) |
| Immunocompromised | 953 (1.3%) | 10 | 2.1 (0.1–4.2) | 2.46 (1.31– 4.61) | 2.48 (1.31– 4.68) | 2.36 (1.04–5.36) |
| Date of initial infection | ||||||
| March–May 2020 | 8545 (11.4%) | 62 | 0.2 (0.1–0.3)a | 1.0 (ref) | 1.0 (ref) | 1.0 (ref) |
| June–August 2020 | 49 887 (66.4%) | 218 | 0.3 (0.2–0.3)a | 1.28 (0.90– 1.82) | 1.32 (0.92–1.89) | 1.43 (0.93–2.18) |
| September–October 2020 | 16 717 (22.2%) | 35 | 0.4 (0.2–0.5)a | 2.13 (1.30– 3.48) | 2.26 (1.38–3.71) | 0.92 (0.27–3.12) |
| Hospitalized at initial infection | ||||||
| Hospitalized | 4094 (5.4%) | 29 | 1.2 (0.6–1.7) | 1.52 (1.04–2.24) | 1.60 (1.07–2.38) | 1.29 (0.76–2.19) |
| Non-hospitalized | 71 055 (94.6%) | 286 | 0.8 (0.7–1.0) | 1.0 (ref) | 1.0 (ref) | 1.0 (ref) |
Adjusted models include all factors in the table, mutually adjusted for each other.
a
Estimate at 150 days due to insufficient follow-up for 270-day estimate in later groups.
b
Diagnosed with HIV/AIDS, leukaemia, lymphoma, congenital immunodeficiencies, asplenia or hyposplenia prior to initial infection.
c
Sensitivity analysis defining reinfection as a positive test ≥120 days after initial infection instead of ≥90 days, as in the primary analysis.