Effectiveness of a earlier an infection in stopping re-infection with Omicron and different SARS-CoV-2 variants in Qatar

In a examine lately revealed on the preprint server medRxiv *, researchers estimate the effectiveness of a earlier an infection in stopping reinfection (PE) with Omicron and different variants of coronavirus 2 of extreme acute respiratory syndrome (SARS-CoV-2) for the resident inhabitants from Qatar one.

Examine: Pre-infection safety in opposition to SARS-CoV-2 reinfection with the Omicron variant. Picture supply: creativeneko / Shutterstock

A earlier SARS-CoV-2 an infection creates sturdy safety in opposition to renewed an infection with the variants Alpha (B.1.1.7), Beta (B.1.351) and Delta (B.1.617.2). Nonetheless, this doesn’t apply to the Omicron (B.1.1.529) variant, which carries a number of mutations in its spike protein that mediate immune evasion.

Concerning the examine

PEs are the proportional discount in susceptibility to an infection with Coronavirus Illness 2019 (COVID-19) in folks with a earlier an infection in comparison with individuals who weren’t beforehand contaminated with SARS-CoV-2. The researchers within the current examine estimated PEs with Omicron and different SARS-CoV-2 variants in Qatar utilizing the test-negative case-control examine design, a validated methodology for sturdy estimates of PEs, to look at the safety afforded by earlier ones SARS-CoV-2 an infection to stop reinfection with SARS-CoV-2 variants.

The info supply for the current examine was Qatar’s nationwide, federated SARS-CoV-2 databases, which supplied particulars on all COVID-19 polymerase chain response (PCR) take a look at circumstances, vaccinations, medical infections, hospital admissions, deaths and comparable demographics . Whereas virtually everybody in Qatar was vaccinated on the time of the examine, the vaccination playing cards of individuals arriving from different international locations had been additionally recorded in Qatar’s SARS-CoV-2 databases on the airport.

PEs had been estimated for the alpha, beta, and delta variants in sufferers recognized between March 23, 2021 and November 18, 2021. Each PCR-positive circumstances with genotyped variant an infection, confirmed by real-time reverse transcription PCR (RT-qPCR), the genotyping of the optimistic medical samples and the controls in a ratio of 1: 5 in response to gender, 10-year age group, nationality and calendar week of the PCR take a look at precisely matched so as to management recognized variations or biases within the danger of publicity to SARS-CoV-2 an infection.

Equally, PEs for the Omicron variant had been estimated in sufferers recognized between December 23, 2021 and January 2, 2022. Each Omicron-infected COVID-19 circumstances and controls had been matched in a ratio of 1: 3 by gender and 10-year age group, nationality and calendar day of the PCR take a look at.

COVID-19 reinfections with negligible signs and excessive Ct values ​​should not important from a public well being perspective. Due to this fact, the examine solely targeted on assessing PEs in opposition to reinfections with an RT-qPCR cycle threshold (Ct) of ≤ 30.

The researchers additionally carried out two sensitivity analyzes to test the robustness of the examine estimates of PEs. Within the first evaluation, the vaccination standing was additionally adjusted, and within the second evaluation, folks with a vaccination card previous to the PCR take a look at had been excluded.


Within the current examine, the estimated PEs had been one minus the ratio of the chance of prior an infection in PCR optimistic circumstances to the chance of prior an infection within the controls. Earlier an infection means a PCR-confirmed an infection 90 days earlier than a brand new PCR-positive take a look at.

The examine outcomes confirmed PEs of 90.2% for Alpha, 84.8% for Beta, 92.0% for Delta, and 56.0% for Omicron. Of all circumstances of COVID-19 reinfections, just one alpha, two beta, zero-delta, and two omicron reinfections resulted in extreme COVID-19, whereas none resulted in vital or deadly COVID-19. The median time between earlier an infection and PCR take a look at for circumstances and controls for the alpha, beta, delta, and omicron variants had been 279, 284,253, and 314 days, respectively.

Every examine participant who examined optimistic in a PCR take a look at and was hospitalized underwent an an infection severity evaluation each three days till discharge or demise. This severity, criticality, and mortality evaluation protocol was utilized to all alpha, beta, and delta circumstances, however solely to a small variety of Omicron circumstances. The outcomes estimated PEs in opposition to hospitalization or demise from reinfection at 69.4% for Alpha, 88.0% for Beta, 100% for Delta, and 87.8% for Omicron.


In abstract, it may be stated that the examine outcomes projected a safety of ~ 90% in opposition to SARS-CoV-2 alpha, beta or delta variants that had been mediated by a earlier SARS-CoV-2 + an infection whereas he was in opposition to Omicron was significantly decrease at virtually 60%. Whatever the variant, the earlier an infection additionally gives sturdy safety in opposition to hospitalization or demise within the occasion of reinfection.

As a result of Qatar has an unusually younger and various demographics, the examine outcomes might not apply to different international locations the place aged residents make up a big proportion of the inhabitants. Qatar has solely 9% of the inhabitants over the age of fifty and 89% of the inhabitants are expatriates from over 150 international locations.

*Vital NOTE

medRxiv publishes preliminary scientific experiences that haven’t been peer-reviewed and subsequently shouldn’t be thought of conclusive, that information medical follow / health-related habits or needs to be handled as established data.

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