Table 2. Characteristics of Individuals With Breakthrough Infection and Nonbreakthrough Infection in Cohort 1 After the Emergence of the Delta Variant (July 1 to November 6, 2021).
| Characteristic | Breakthrough infection (n = 49) | Nonbreakthrough infection (n = 34)a | P value |
|---|---|---|---|
| Age, median (IQR), y | 43 (31-59) | 44 (32-56) | .65 |
| Sex | |||
| Male | 22 (45) | 10 (29) | .15 |
| Female | 27 (55) | 24 (71) | |
| Participant type, No. (%) | |||
| Health care worker | 42 (86) | 18 (53) | .003 |
| Patient | 6 (12) | 10 (29) | |
| Guardian or caregiver | 1 (2) | 6 (18) | |
| Time from second vaccination to diagnosis, median (IQR), d | 98 (57-143) | NA | NA |
| Type of COVID-19 vaccine, No. (%) | |||
| ChAdOx1 nCoV-19 | 40 (82) | NA | NA |
| BNT162b2 | 5 (10) | NA | |
| mRNA-1273 | 2 (4) | NA | |
| Heterologousb | 2 (4) | NA | |
| Symptomatic at diagnosis, No. (%) | 37 (76) | 21 (62) | .23 |
| Time from symptom onset to diagnosis, median (IQR) | 1 (0-2) | 1 (0-2) | .21 |
| Ct value at diagnosis, median (IQR) | 19 (16-26)c | 25 (18-32)d | .04 |
| Nosocomial secondary transmission, No./total No. (%)e | 3/43 (7) | 7/28 (25) | .04 |
Abbreviations: Ct, cycle threshold; mRNA, messenger RNA; NA, not applicable.
a
Including 14 partially vaccinated individuals.
b
ChAdOx1 nCoV-19 followed by BNT162b2.
c
Including 44 individuals who underwent SARS-CoV-2 testing at our hospital; Ct values were unavailable in the remaining 5 individuals.
d
Including 28 individuals who underwent SARS-CoV-2 testing at our hospital; Ct values were unavailable in the remaining 6 individuals.
e
Excluding individuals who were diagnosed during quarantine (6 in the breakthrough infection group and 6 in the nonbreakthrough infection group).