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. 2021 Oct 5;73(7):e1830-e1840.
doi: 10.1093/cid/ciaa1846.

Assessment of the Risk of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Reinfection in an Intense Reexposure Setting

Laith J Abu-Raddad  1   2   3 , Hiam Chemaitelly  1   2 , Joel A Malek  4   5 , Ayeda A Ahmed  4 , Yasmin A Mohamoud  4 , Shameem Younuskunju  4 , Houssein H Ayoub  6 , Zaina Al Kanaani  7 , Abdullatif Al Khal  7 , Einas Al Kuwari  7 , Adeel A Butt  7 , Peter Coyle  7 , Andrew Jeremijenko  7 , Anvar Hassan Kaleeckal  7 , Ali Nizar Latif  7 , Riyazuddin Mohammad Shaik  7 , Hanan F Abdul Rahim  8 , Hadi M Yassine  9   10 , Mohamed G Al Kuwari  11 , Hamad Eid Al Romaihi  12 , Mohamed H Al-Thani  12 , Roberto Bertollini  12
Affiliations

Assessment of the Risk of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Reinfection in an Intense Reexposure Setting

Laith J Abu-Raddad et al. Clin Infect Dis. .

Abstract

Background: Risk of reinfection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is unknown. We assessed the risk and incidence rate of documented SARS-CoV-2 reinfection in a cohort of laboratory-confirmed cases in Qatar.

Methods: All SARS-CoV-2 laboratory-confirmed cases with at least 1 polymerase chain reaction-positive swab that was ≥45 days after a first positive swab were individually investigated for evidence of reinfection. Viral genome sequencing of the paired first positive and reinfection viral specimens was conducted to confirm reinfection.

Results: Out of 133 266 laboratory-confirmed SARS-CoV-2 cases, 243 persons (0.18%) had at least 1 subsequent positive swab ≥45 days after the first positive swab. Of these, 54 cases (22.2%) had strong or good evidence for reinfection. Median time between the first swab and reinfection swab was 64.5 days (range, 45-129). Twenty-three of the 54 cases (42.6%) were diagnosed at a health facility, suggesting presence of symptoms, while 31 (57.4%) were identified incidentally through random testing campaigns/surveys or contact tracing. Only 1 person was hospitalized at the time of reinfection but was discharged the next day. No deaths were recorded. Viral genome sequencing confirmed 4 reinfections of 12 cases with available genetic evidence. Reinfection risk was estimated at 0.02% (95% confidence interval [CI], .01%-.02%), and reinfection incidence rate was 0.36 (95% CI, .28-.47) per 10 000 person-weeks.

Conclusions: SARS-CoV-2 reinfection can occur but is a rare phenomenon suggestive of protective immunity against reinfection that lasts for at least a few months post primary infection.

Keywords: SARS-CoV-2; epidemiology; genetics; immunity; reinfection.

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Figures

Figure 1.
Figure 1.
Distribution of the time difference between the first swab and subsequent swabs among all laboratory-confirmed severe acute respiratory syndrome coronavirus 2 cases with more than 1 positive swab. The cutoff of 45 days was at the 99th percentile and thus provides an appropriate mark for defining the end of the prolonged polymerase chain reaction positivity.
Figure 2.
Figure 2.
Flow chart describing the selection process of SARS-CoV-2 eligible cases and summarizing the results of their reinfection status evaluation. Abbreviations: Ct, cycle threshold; PCR, polymerase chain reaction; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.
Figure 3.
Figure 3.
Viral genome sequencing analysis of the paired viral specimens of the first positive and reinfection swabs for the 6 patients with conclusive or supporting evidence for reinfection or no reinfection.
See this image and copyright information in PMC

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