Table 3.
Rates of previously infected (PI) individuals in cohorts infected with different variants of SARS-CoV-2 (regardless of the vaccination status)
| Study | Country/Study type | Description | Negative cohorts % (n/N) |
Delta (or other) infected cohorts % (n/N) |
Omicron infected cohorts % (n/N) or % (n) |
P value |
|---|---|---|---|---|---|---|
| Lewnard et al. [58] |
USA Cohort study |
15 December 2021 to 17 January 2022 (Documented PI) |
- |
0.4% (84/23305) |
0.5% (1,163/222688) |
NR |
|
3 February to 17 March 2022 (Documented PI) |
- | - |
0.6% (75/12756) BA.1 0.4% (7/1905) BA.2 |
NR | ||
| Stegger et al. [59] |
Denmark Danish COVID-19 surveillance |
Rate of second infection when PI with BA.1 | - | 0% (0/263) |
6.46% (17/263) BA.1 17.87% (47/263) BA.2 |
NR |
| Rate of second infection when PI with BA.2 | - | 0% (0/263) |
0% (0/263) BA.1 1.14% (3/263) BA.2 |
NR | ||
| Rate of second infection when PI with Delta | - | 11.4% (30/263) |
9.88% (26/263) BA.1 53.23% (140/263) BA.2 |
NR | ||
| Rate of second infection when PI (overall) | - | 11.4% (30/263) |
12.54% (33/263) BA.1 72.24% (190/263) BA.2 |
NR | ||
| Andrews et al. [60] |
UK Test-negative case–control |
Rate of PI out of the Delta and Omicron | 16.5% (260,073/1572621) | 1.8% (3,754/204154) | 11.1% (98,150/886774) | NR |
| Espenhain et al. [38] |
Denmark Data from the routine Danish surveillance of COVID-19 |
PI | - | 0.9% (160/19137) | 4.3% (34/785) | NR |
| Davies et al. [42] |
South Africa Cohort study |
HR for PI (vs. None) | - | - |
Death 1.10 (0.63—1.92) Severe hospitalization or death 0.60 (0.37—0.98) Hospitalization or death 0.28 (0.19—0.40) |
- |
| PI | - |
Wave 3 (Delta, 20/5/2021 to 23/6/2021) 3.2% (140/4403) |
Wave 4 (Omicron, 14/11/2021 to 11/12/2021) 11.3% (580/5144) |
- | ||
| Peralta-Santos et al. [49] |
Portugal Cohort Study National network group of laboratories |
PI | - | 1.6% (146/9397) | 6.8% (449/6581) | < 0.001 |
| Wolter et al. [51] |
South Africa Data linkage study |
aPI | - | 4.5% (43/948) (non SGTF) |
10.4% (1100/10 547) (SGTF) |
0.18 |
| Ward et al. [52] |
UK Data linkage aPI |
PI | - | 1% (2211/221146) | 6.6% (53,724/814003) | NR |
| Garg et al. [53] |
India Cohort study |
PI | - | 8.2% (6/182) | 17.1% (14/82) | NR |
| Krutikov et al. [54] |
UK Prospective cohort study |
PI | - |
Pre-Omicron 4.3% (17/400) |
12.7% (236/1864) | < 0.0001 |
| Shrestha et al. [36] |
USA Retrospective cohort study |
PI | - | - |
2.9% (88/4585) symptomatic 1.5% (2/133) hospitalized |
- |
| Hajjo et al. [47] |
Jordan Questionnaire based study |
Reinfected within 90 days | - | - |
8.6% (43/500) of which: 41.9% (18/43) asymptomatic 44.2% (19/43) mild 2.3% (1/43) moderate 2.3% (1/43) severe 9.3% (4/43) unspecified |
- |
| Smith-Jeffcoat et al. [37] |
USA Cohort (convention attendees) |
PI | 0% (0/7) | - | 6.25% (1/16) | NR |
| Sharma et al. [40] |
Rajasthan, India Cohort study |
PI | - | - | 43.2% (126) | - |
| MMWR [43] |
USA Cohort study |
PI | - | - | 14% (6/43) | - |
| Madhi et al. [44] |
South Africa seroepidemiologic survey |
PI | - | - | 2.8% (195) | - |
| Maisa et al. [48] |
France Questionnaire based |
PI | - | - |
14% (39/278) 2% hospitalized (7/294) – of these 7, 2 PI |
- |
| Qassim et al. [50] |
Qatar Cross sectional study |
No PI | - | - | 90.8% (141,839) | - |
| PI < 90 days before the study | - | - | 0.4% (560) | - | ||
| PI overall | - | - | 8.8% (13,803) | - |
N: Total number of subjects in the cohort
n: number of subjects who were PI or as specified in each row
SGTF samples with S gene target failure (strongly indicative of an Omicron variant)
aReinfection was defined by an individual having at least one positive SARS-CoV-2 test more than 90 days before the current positive test