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Estimation of the Seroprevalence and Infection Fatality Rate of the SARS-CoV-2 Omicron Variant Using Antibody Screening of Danish Blood Donors

24 Pages Posted: 16 May 2022

See all articles by Christian Erikstrup

Christian Erikstrup

Aarhus University - Department of Clinical Immunology

Anna Damkjær Laksafoss

Statens Serum Institut

Josephine Gladov

Aarhus University - Department of Clinical Immunology

Kathrine Agergård Kaspersen

Aarhus University - Department of Clinical Immunology

Susan Mikkelsen

Aarhus University - Department of Clinical Immunology

Lotte Hindhede

Aarhus University - Department of Clinical Immunology

Jens Kjærgaard Boldsen

Aarhus University - Department of Clinical Immunology

Signe Winther Jørgensen

Aarhus University - Department of Clinical Immunology

Steen Ethelberg

Statens Serum Institut - Infectious Disease Epidemiology & Prevention

Dorte Kinggaard Holm

Odense University Hospital - Department of Clinical Immunology

Mie Topholm

Odense University Hospital - Department of Clinical Immunology

Janna Nissen

University of Copenhagen - Department of Clinical Immunology

Michael Schwinn

University of Copenhagen - Department of Clinical Immunology

Thorsten Brodersen

Zealand University Hospital - Department of Clinical Immunology

Christina Mikkelsen

University of Copenhagen - Department of Clinical Immunology

Susanne Gjørup Sækmose

Zealand University Hospital - Department of Clinical Immunology

Erik Sørensen

University of Copenhagen - Department of Clinical Immunology

Lene Holm Harritshøj

University of Copenhagen - Department of Clinical Immunology

Bitten Aagaard

Aalborg University Hospital - Department of Clinical Immunology

Khoa Manh Dinh

Aarhus University - Department of Clinical Immunology

Michael Busch

Vitalant Research Institute

Charlotte S. Jørgensen

Statens Serum Institut

Tyra Grove Krause

Statens Serum Institut

Henrik Ullum

Statens Serum Institut

Sisse Rye Ostrowski

University of Copenhagen - Department of Clinical Medicine

Laura Espenhain

Statens Serum Institut - Infectious Disease Epidemiology & Prevention

Ole Birger Pedersen

Zealand University Hospital - Department of Clinical Immunology

More...

Abstract

Background: Introduction of the Omicron variant caused a steep rise in SARS-CoV-2 infections despite high vaccination-coverage in the Danish population. We used blood donor serosurveillance to estimate the percentage of the population with recent infection.

Methods: To detect SARS-CoV-2 antibodies induced due to recent infection, and not vaccination, we assessed anti-nucleocapsid (anti-N) immunoglobulin G (IgG) in blood donor samples. Individual level data on SARS-CoV-2 RT-PCR results and vaccination status were available. Anti-N IgG was measured fortnightly from January 18 to April 3, 2022. Samples from November 2021 were analysed to assess seroprevalence before introduction of the Omicron variant in Denmark.

Findings: A total of 43 088 donations from 35 309 Danish blood donors aged 17–72 years were screened. In November 2021, 1∙2 % of donors had detectable anti-N IgG antibodies. With adjustment for test sensitivity (estimates ranging from 74%–81%) and November seroprevalence, we estimate that 68% (95% confidence intervals (CI): 64%–71%) of the healthy adult Danish population had been infected with SARS-CoV-2 between November 1, 2021, and March 15, 2022. One third of infections were not captured by SARS-CoV-2 RT-PCR testing. The infection fatality rate (IFR) among the healthy adult Danish population was 6 (CI: 5–7) per 100 000 infections.

Interpretation: Screening for anti-N IgG and linkage to national registers allowed us to detect recent infections and accurately assess assay sensitivity in vaccinated or previously infected individuals during the Omicron outbreak. The IFR was lower than during previous waves.

Funding: The Danish Ministry of Health

Declaration of Interest: The authors declare no conflict of interests

Ethical Approval: The study was approved as a surveillance study in all five Danish administrative regions and the appropriate institutional forms obtained

Suggested Citation

Erikstrup, Christian and Damkjær Laksafoss, Anna and Gladov, Josephine and Agergård Kaspersen, Kathrine and Mikkelsen, Susan and Hindhede, Lotte and Kjærgaard Boldsen, Jens and Winther Jørgensen, Signe and Ethelberg, Steen and Kinggaard Holm, Dorte and Topholm, Mie and Nissen, Janna and Schwinn, Michael and Brodersen, Thorsten and Mikkelsen, Christina and Gjørup Sækmose, Susanne and Sørensen, Erik and Holm Harritshøj, Lene and Aagaard, Bitten and Dinh, Khoa Manh and Busch, Michael and Jørgensen, Charlotte S. and Grove Krause, Tyra and Ullum, Henrik and Ostrowski, Sisse Rye and Espenhain, Laura and Pedersen, Ole Birger, Estimation of the Seroprevalence and Infection Fatality Rate of the SARS-CoV-2 Omicron Variant Using Antibody Screening of Danish Blood Donors. Available at SSRN: https://ssrn.com/abstract=4111171 or http://dx.doi.org/10.2139/ssrn.4111171

Christian Erikstrup (Contact Author)

Aarhus University - Department of Clinical Immunology ( email )

Aarhus
Denmark

Anna Damkjær Laksafoss

Statens Serum Institut ( email )

Denmark

Josephine Gladov

Aarhus University - Department of Clinical Immunology ( email )

Kathrine Agergård Kaspersen

Aarhus University - Department of Clinical Immunology ( email )

Susan Mikkelsen

Aarhus University - Department of Clinical Immunology ( email )

Aarhus
Denmark

Lotte Hindhede

Aarhus University - Department of Clinical Immunology ( email )

Jens Kjærgaard Boldsen

Aarhus University - Department of Clinical Immunology ( email )

Signe Winther Jørgensen

Aarhus University - Department of Clinical Immunology ( email )

Steen Ethelberg

Statens Serum Institut - Infectious Disease Epidemiology & Prevention ( email )

Dorte Kinggaard Holm

Odense University Hospital - Department of Clinical Immunology ( email )

Mie Topholm

Odense University Hospital - Department of Clinical Immunology ( email )

Odense
Denmark

Janna Nissen

University of Copenhagen - Department of Clinical Immunology ( email )

Michael Schwinn

University of Copenhagen - Department of Clinical Immunology ( email )

Thorsten Brodersen

Zealand University Hospital - Department of Clinical Immunology ( email )

Christina Mikkelsen

University of Copenhagen - Department of Clinical Immunology ( email )

Susanne Gjørup Sækmose

Zealand University Hospital - Department of Clinical Immunology ( email )

Erik Sørensen

University of Copenhagen - Department of Clinical Immunology ( email )

Denmark

Lene Holm Harritshøj

University of Copenhagen - Department of Clinical Immunology ( email )

Bitten Aagaard

Aalborg University Hospital - Department of Clinical Immunology ( email )

Khoa Manh Dinh

Aarhus University - Department of Clinical Immunology ( email )

Aarhus
Denmark

Michael Busch

Vitalant Research Institute ( email )

San Francisco, 94118
United States

Charlotte S. Jørgensen

Statens Serum Institut ( email )

Denmark

Tyra Grove Krause

Statens Serum Institut ( email )

Denmark

Henrik Ullum

Statens Serum Institut ( email )

Sisse Rye Ostrowski

University of Copenhagen - Department of Clinical Medicine ( email )

Nørregade 10
Copenhagen, København DK-1165
Denmark

Laura Espenhain

Statens Serum Institut - Infectious Disease Epidemiology & Prevention ( email )

Copenhagen
Denmark

Ole Birger Pedersen

Zealand University Hospital - Department of Clinical Immunology ( email )

Køge
Denmark

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