In Denmark, Omicron reinfections reveal ineffective post-COVID-19 immunity


In a latest research posted to the medRxiv* preprint server, researchers investigated variant-wise SARS-CoV-2 reinfection circumstances in Denmark.

The evolution of SARS-CoV-2 has led to the emergence of a number of variants of concern (VOC) with elevated transmissibility and immune-evasiveness reminiscent of Omicron, resulting in an upsurge of SARS-CoV-2 reinfections and difficulties in COVID-19 mitigation globally. Research have investigated SARS-CoV-2 reinfection frequencies however had been restricted to reverse transcriptase polymer chain response (RT-PCR) evaluation information, wherein SARS-CoV-2 Pango lineages aren’t specified. As well as, a genomic sequencing report is usually categorized as both preliminary an infection or reinfection, however next-generation sequencing (NGS) information for an preliminary an infection and reinfection are hardly ever reported collectively for a person.

Research: Increasing Cases of SARS-CoV-2 Omicron Reinfection Reveals Ineffective Post-COVID-19 Immunity in Denmark and Conveys the Need for Continued Next-Generation Sequencing. Picture Credit score: Noiel / Shutterstock

In regards to the research

Within the current research, researchers characterised SARS-CoV-2 reinfections by variant based mostly on the combination of RT-PCR evaluation and next-genome sequencing (NGS) evaluation of sequences obtained from Danish SARS-CoV-2-positive people and the GISAID (international initiative on sharing avian influenza information) database.

NGS information and scientific metadata of major SARS-CoV-2 infections and reinfections from the identical particular person residing in Denmark had been analyzed. In complete, 21,708 entries of reinfections had been out there between 1 March 2020 and 28 August 2022, with information on the dates of pattern assortment about major SARS-CoV-2 infections and reinfections.

The workforce documented scientific SARS-CoV-2 metadata because the time factors of preliminary and subsequent SARS-CoV-2 infections to measure the length between the preliminary and subsequent SARS-CoV-2 infections. As well as, RT-PCR evaluation outcomes and NGS evaluation outcomes had been out there for major infections and reinfections, respectively. 

The workforce excluded 70 case entries (<one % of complete circumstances) (n=70) with similar Pango lineages for major infections and reinfections since such entries could possibly be consultant of unresolved SARS-CoV-2 infections as an alternative of reinfections. As well as, Beta, Gamma, and ‘different’ (with out universally acceptable Pango nomenclature) VOC information had been excluded resulting from low sequence ranges.

Reinfection circumstances had been stratified by variant and subvariant. The GISAID database was accessed for 2 information: one set of information comprising present metadata for >12 million SARS-CoV-2 sequences and the second set comprising filtered metadata information of solely Denmark residents with two related SARS-CoV-2 infections documented.


Major an infection and reinfection with Omicron (i.e., Omicron-Omicron infections) had been reported to happen inside a brief interval (even inside three weeks, a mean of twenty-two weeks) than non-Omicron-Omicron infections. Omicron reinfections inside ten weeks of preliminary Omicron an infection had been largely reported resulting from BA.1 adopted by BA.2.

Reinfection frequency was considerably greater with Omicron (25%, N=1875) after major infections with any VOC. No Alpha VOC-induced reinfection circumstances had been reported, whereas Delta VOC precipitated reinfections in 2.3% (n=169) of circumstances. Pre-Omicron estimates of pure infection-induced immunity had been above 90%, which dropped to beneath 10% in three to 4 months.

Amongst people with Delta-induced major infections, reinfections resulting from Delta variant <1% (n=18) however for Omicron reinfections had been 41% (n=3060 circumstances). Additional, reinfections with the identical VOC however differing subvariants had been solely 0.3% (n=24), apart from Omicron (4.6%, n=340). 93% of people reinfected from March 2020 had Omicron reinfections, indicating that preliminary SARS-CoV-2 an infection with the Wuhan-Hu-1 pressure, Alpha VOC, or Delta VOC variant was unable to confer sufficient immune safety towards reinfections, particularly for Omicron reinfections.

Omicron reinfections had been reported amongst 62% (n=211), 20%, (n=68), and 30% (n=102) of circumstances wherein major SARS-CoV-2 infections had been brought on by Omicron BA.1, BA.2, and BA.5, respectively, People with major BA.2 infections demonstrated excessive reinfection frequencies (38%, n=129) with the Omicron BA.5 subvariant (26%, n=89). The findings indicated that despite the fact that the SARS-CoV-2 spike (S) protein of the three Omicron subvariants are related, variations within the Omicron subvariants had been sufficient to stop Omicron BA.1/2 infection-induced nAbs (neutralizing antibodies) from binding with Omicron BA.5 S.


The research findings confirmed that almost all SARS-CoV-2 reinfection circumstances occurred resulting from Omicron. Omicron reinfections amongst these with major Omicron an infection occurred inside a brief interval, as much less as three weeks. The findings indicated that major infections with non-Omicron VOCs had been insufficient in offering immune safety to stop reinfections with Omicron.

Additional, the findings spotlight the transmissibility and immune-evasiveness of Omicron and the necessity for up to date SARS-CoV-2 vaccines, continued SARS-CoV-2 surveillance, and SARS-CoV-2 evolutionary assessments to information policy-making for improved public well being throughout the globe. As well as, the evaluation underscores the necessity for analyzing individual-level NGS information to supply exact estimates of SARS-CoV-2 reinfection dangers.

*Necessary discover

medRxiv publishes preliminary scientific experiences that aren’t peer-reviewed and, due to this fact, shouldn’t be considered conclusive, information scientific apply/health-related habits, or handled as established info.

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