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. 2022 Sep 30;29(8):taac109. doi: 10.1093/jtm/taac109

Table 2.

Hazard ratios for the incidence of SARS-CoV-2 infection and incidence of severe, critical or fatal COVID-19 in the Pre-Omicron Reinfection Study, Omicron Reinfection Study and COVID-19 Severity Reinfection Study

Epidemiological measure Primary-infection cohort Infection-naïve cohort
Pre-Omicron Reinfection Study
Primary outcome
Total follow-up time (person-weeks) 6 578 466 6 432 430
Incidence rate of infection (per 10 000 person-weeks) 2.8 (2.6–2.9) 18.6 (18.3–18.9)
Unadjusted hazard ratio for SARS-CoV-2 infection (95% CI) 0.15 (0.14–0.15)
Adjusted hazard ratio for SARS-CoV-2 infectiona (95% CI) 0.14 (0.14–0.15)
Effectiveness against SARS-CoV-2 infection in % (95% CI) 85.5 (84.8–86.2)
Secondary outcome
Unadjusted hazard ratio for severe, critical or fatal COVID-19b (95% CI) 0.02 (0.01–0.04)
Adjusted hazard ratio for severe, critical or fatal COVID-19a,b (95% CI) 0.02 (0.01–0.04)
Effectiveness against severe, critical or fatal COVID-19a,b (95% CI) 98.0 (95.7–99.0)
Omicron Reinfection Study
Primary outcome
Total follow-up time (person-weeks) 2 493 870 2 411 571
Incidence rate of infection (per 10 000 person-weeks) 32.1 (31.4–32.8) 50.7 (49.8–51.6)
Unadjusted hazard ratio for SARS-CoV-2 infection (95% CI) 0.64 (0.62–0.66)
Adjusted hazard ratio for SARS-CoV-2 infectiona (95% CI) 0.62 (0.60–0.64)
Effectiveness against SARS-CoV-2 infection in % (95% CI) 38.1 (36.3–39.8)
Secondary outcome
Unadjusted hazard ratio for severe, critical or fatal COVID-19b (95% CI) 0.13 (0.05–0.33)
Adjusted hazard ratio for severe, critical or fatal COVID-19a,b (95% CI) 0.11 (0.04–0.29)
Effectiveness against severe, critical or fatal COVID-19a,b (95% CI) 88.6 (70.9–95.5)
Reinfection COVID-19 Severity Study
Primary outcome
Total follow-up time (person-weeks) 9 290 507 9 022 235
Incidence rate of severe, critical or fatal COVID-19 (per 10 000 person-weeks) 0.01 (0.01–0.02) 0.40 (0.36–0.44)
Unadjusted hazard ratio for severe, critical or fatal COVID-19b (95% CI) 0.03 (0.01–0.05)
Adjusted hazard ratio for severe, critical or fatal COVID-19a,b (95% CI) 0.03 (0.01–0.05)
Effectiveness against severe, critical or fatal COVID-19a,b (95% CI) 97.3 (94.9–98.6)
Secondary outcome
Unadjusted hazard ratio for SARS-CoV-2 infection (95% CI) 0.31 (0.30–0.32)
Adjusted hazard ratio for SARS-CoV-2 infectiona (95% CI) 0.31 (0.30–0.31)
Effectiveness against SARS-CoV-2 infection in % (95% CI) 69.4 (68.6–70.3)

CI denotes confidence interval, COVID-19 coronavirus disease 2019, and SARS-CoV-2 severe acute respiratory syndrome coronavirus 2.

a

Cox regression analysis adjusted for sex, 10-year age group (Table 1), 10 nationality groups (Table 1), comorbidity count (Table 1) and calendar week of the SARS-CoV-2 test.

b

Severity,23 criticality23 and fatality24 were defined according to the World Health Organization guidelines.