|
Total size (enrolled; before exclusions) |
Time
period |
Reported lineage |
Reported outcome measure
(protection, risk, reinfection rate) |
Repeat infection outcome
(selected comparisons, terminology as reported) |
Severe
COVID-19 outcome (selected comparisons, terminology as
reported) |
Primary publications |
Primary publications |
Primary publications |
Primary publications |
Primary publications |
Primary publications |
Primary publications |
Hansen et al. 2021
Non-vaccinated individuals
Denmark
(141)
|
~ 4 million individuals
|
Feb 26, 2020–Dec 31, 2020
|
None
|
Protection
|
Protection against repeat infection in those11Derived as 1− adjusted relative risk. The rates of
infection during the second surge were compared across those with a
positive or negative PCR test from the first surge. The calculated the
rate of infection was calculated as the number of individuals with
positive PCR tests during the second surge divided by the cumulative
number of person-days at risk
< 65 years:
80.5% (95% CI 75.4–84.5)
≥ 65 years:
47.1% (96% CI 24.7–62.8)
|
Not assessed
|
Abu-Raddad et al. 2021
Non-vaccinated individuals22Qatar launched its vaccination campaign on December 21,
2020, around the time this study was concluded (December 31, 2020), so
very few individuals had been vaccinated at time of this study.
Qatar
(142)
|
192,984 individuals
|
April 16, 2020–Dec 31, 2020
|
None
|
Protection
|
Efficacy of natural infection against reinfection33Derived as 1− the ratio of the incidence rate of
reinfection in the antibody-positive cohort to the incidence rate of
infection in the antibody-negative cohort.
95.2% (95% CI: 94.1–96.0)
|
Not assessed
Of 129 cases with good or some evidence of reinfection, one
reinfection was severe, two were moderate, and none were critical or
fatal
|
Hall et al. 2021
Non-vaccinated and vaccinated individuals
UK
(143)
|
30,625 individuals
|
June 18, 2020–Jan 11, 2021
|
Not specified
B.1.1.7
|
Risk
|
Risk of reinfection causing44Derived as 1− adjusted incident rate ratio.
COVID-19 symptoms:
aIRR 0.074 (95% CI 0.06–0.10)
All events (COVID-19 symptoms, other symptoms, asymptomatic):
aIRR 0.159 (95% CI 0.13–0.19)
|
Not assessed
|
Lumley et al. 2022
Non-vaccinated and vaccinated individuals
UK
(144)
|
13,109 individuals
|
March 27, 2020–Feb 28, 2021
|
Non-S-gene target failure
B.1.1.7
|
Risk
|
Risk of PCR-positive result (symptomatic or asymptomatic) in
Unvaccinated seropositive55Compared incidence in each follow-up group to unvaccinated
seronegative healthcare workers.:
aIRR 0.02 (95% CI 0.01–0.18)
|
Not assessed
|
Abu-Raddad et al. 2021
Non-vaccinated and vaccinated individuals
Qatar
(145)
|
193,233 individuals
|
Before Nov 1, 2020–March 3, 2021
|
B.1.1.7
Variants of unknown status
|
Protection
|
Efficacy of natural infection against reinfection
with66Derived as 1− the ratio of the incidence rate of
reinfection in the PCR-confirmed (or antibody-positive) cohort to the
incidence rate of infection in the antibody-negative cohort.
B.1.1.7, prior PCR-confirmed infection:
97.5% (95% CI 95.7–98.6)
B.1.1.7, prior antibody-positive result:
97.0% (95% CI 92.5–98.7)
Unknown variant, prior PCR-confirmed infection: 92.2% (95% CI:
90.6–93.5)
Unknown variant, prior antibody-positive result: 94.2% (95% CI:
91.8–96.0)
|
Not assessed
|
Chemaitelly, H et al. 2021
Unvaccinated individuals
(146)
Qatar
|
380,914 individuals
|
Before Jan 1, 2021–April 21, 202177This timeframe coincided with the beginning of the decline
of the B.1.1.7 wave and the rapid expansion of the B.1.351 wave that
peaked early April 2021.
|
B.1.351
B.1.1.7
Variants of unknown status
|
Protection
|
Efficacy of natural infection against reinfection
with88Derived as 1− the ratio of the incidence rate of
reinfection in the cohort of individuals with a prior PCR-confirmed
infection to the incidence rate of infection in the antibody-negative
cohort.
B.1.351:
92.3% (95% CI: 90.3–93.8)
B.1.1.7:
97.6% (95% CI 95.7–98.7)
Variants of unknown status:
87.9% (95% CI: 84.7–90.5)
|
Not assessed
|
Nordström et al. 2022
Non-vaccinated and vaccinated individuals
Sweden
(147)
|
~3.5 million individuals (3 cohorts)
|
March 20, 2020–Sept 5, 2021
|
Alpha B.1.1.7
Beta B.1.351
Gamma P.1
Delta B.1.617.2
|
Risk
|
Risk of reinfection in those with
Natural immunity99Calculated vs no immunity and after 3 months of follow-up.:
aHR 0.05 (95% CI 0.05–0.05)
One-dose hybrid immunity1010Calculated vs natural immunity and during the first 2
months of follow-up.:
aHR 0.42 (95% CI 0.38–0.47)
One-dose hybrid immunity1111Calculated vs natural immunity and after 2 months of
follow-up.:
aHR 0.55 (95% CI 0.39–0.76)
Two-dose hybrid immunity, overall1212Calculated vs natural immunity.:
aHR 0.34 (95% CI 0.31–0.39)
|
Risk of hospitalization (HR)
Two-dose hybrid immunity1313Calculated vs natural immunity.:
0.10 (95% CI 0.04–0.22)
|
Altarawneh et al. 2022
Non-vaccinated and vaccinated individuals
Qatar
(148)
|
~2.3 million individuals
|
March 23, 2021–Nov 18, 2021
|
Alpha
Beta
Delta
Omicron
|
Protection
|
Effectiveness of previous infection in preventing reinfection
with1414Derived as 1− odds ratio of prior infection in cases
(PCR-positive persons with variant infection) versus controls
(PCR-negative persons))
Alpha:
90.2% (95% CI 60.2–97.6)
Beta:
85.7% (95% CI 75.8–to 91.7)
Delta:
92.0% (95% CI 87.9–94.7)
Omicron:
56.0% (95% CI 50.6– 60.9)
|
Effectiveness of previous infection in preventing severe, critical
or fatal disease caused by
Alpha: 69.4% (95% CI −143.6–96.2)
Beta: 88.0% (95% CI 50.7–97.1)
Delta: 100% (95% CI 43.3–100)
Omicron: 87.8% (95% CI 47.5–97.1)
|
Pulliam et al. 2022
Non-vaccinated and vaccinated individuals
South Africa
(149)
|
~2.9 million individuals
|
March 4, 2020–Jan 31, 2022
|
Beta (B.1.351)
Delta (B.1.617.2)
Omicron (B.1.1.529)1515Period of Omicron emergence: November 1, 2021 to November
30, 2021.
|
Risk
|
Risk of reinfection during1616Estimated relative hazard ratios for reinfection during
specified wave versus primary infection during the first wave.
Wave 2 (Beta-driven) versus Wave 1: relative HR 0.71
(95% CI 0.60–0.85)
Wave 3 (Delta-driven) versus Wave 1: relative HR 0.54
(95% CI 0.45–0.64)
Wave 4 (Omicron-driven) versus Wave 1: relative 1.70
(95% CI 1.44–2.04)
|
Not assessed
|
Guedes et al. 2023
Non-vaccinated and vaccinated individuals
Brazil
(150)
|
25,750 real-time RT-PCR tests performed
|
March 10, 2020–March 20, 2022
|
Pre-VOC
Gamma
Delta
Omicron
|
Reinfection rate
|
Reinfection rate during the Omicron variant period:
1717Calculated as number of reinfection cases before and after
the Omicron variant considering the total accumulated number of
SARS-CoV-2 infections in both periods.
Before 0.8% vs after 4.3%;
p<0.001
|
Not assessed
281/281 reinfections were mild
|
Chemaitelly et al. 2022
(151)
Unvaccinated individuals
Qatar
|
Up to 3.3 million individuals
|
Feb 28, 2020– June 5, 20221818Three individual studies (pre-Omicron reinfection, Omicron
reinfection, COVID-19 severity reinfection) spanning different time
periods.
|
Pre-Omicron (ancestral, Alpha, Beta, Delta)
Omicron (BA.1, BA.2, BA.4, BA.5)
|
Protection
|
Effectiveness of pre-Omicron primary infection1919Derived as 1−adjusted hazard ratio, where the hazard ratio
compared incidence of infection in both cohorts. Incidence rate of
infection in each cohort defined as the number of identified
infections divided by the number of person-weeks contributed by all
individuals in the cohort.
Against pre-Omicron reinfection: 85.5% (95% CI: 84.8–86.2%)
Effectiveness peaked at 90.5% (95% CI 88.4–92.3%) in the 7th month
after the primary infection, waning to ~70% by the
16th month
Against Omicron reinfection: 38.1% (95% CI 36.3–39.8%), declining
with time since primary infection
|
Effectiveness of pre-Omicron primary infection2020Cox regression analysis. Severity, criticality, and
fatality defined as per WHO guidelines.
Against severe, critical or fatal COVID-19 due to Omicron
reinfection:
88.6% (95% CI 70.9–95.5)
Against severe, critical, or fatal COVID-19 reinfection (irrespective
of the variant of primary infection or reinfection):
97.3% (95% CI 94.9–98.6)
|
Bowe et al. 2022
Non-vaccinated and vaccinated individuals
USA
(152)
|
~ 5.8 million individuals
|
March 1, 2020–June 25, 2022
|
Pre-Delta
Delta
Omicron
|
Risk
|
Not assessed
|
Risk of all-cause mortality (HR)2121Calculated for reinfection vs no reinfection.
2.17 (95% CI 1.93–2.45)
Risk of hospitalization (HR)
3.32 (95% CI 3.13–3.51)
|
Yang et al. 2023
Non-vaccinated and vaccinated individuals
Malaysia
(153)
|
482 individuals
|
Jan 31, 2022–Jul 31, 20222222The Omicron-dominant period in Malaysia was estimated to
start from early February 2022.
|
Non-Omicron
Omicron
|
Risk
|
Risk of reinfection in those with
Pre-Omicron natural infection2323Calculated vs Omicron-dominant period.: aHR 0.41 (95% CI
0.27–0.62)
|
Not assessed
|
Meta-analyses |
|
|
|
|
|
|
Stein et al 2023.
Global
systematic review and meta-analysis of 65 studies from 19 countries
(154)
|
Various
|
Up to Sept 31, 2022
|
Ancestral
Mixed Alpha (B.1.1.7)
Beta (B.1.351)
Delta (B.1.617.2)
Omicron BA.1 variants
|
Protection
|
Pooled estimate of protection from past infection (with various
variants) against reinfection with
Ancestral:
84.9 (95% UI 72.8–91.8)
Alpha: 90.0% (95% UI 54.8–98.4)
Beta: 85.7% (95% UI 83.4–87.7)
Delta: 82.0 (95% UI 63.5–91.9)
Omicron BA.1: 45.3% (95% UI 17.3–76.1)
|
Pooled estimate of protection against severe disease caused by
Ancestral: 78.1% (95% UI 34.4–96.5)
Alpha: 79.6% (95% UI 43.3–95.3)
Beta: 88% (95% UI 50.7–97.1)2424Single study.
Delta: 97.2% (95% UI 85.2–99.6)
Omicron BA.1: 81.9% (95% UI 73.8–88.0)
|