• Sebastian Weis, André Scherag, Michael Baier, Michael Kiehntopf, Thomas Kamradt, Steffi Kolanos, Juliane Ankert, Stefan Glöckner, Oliwia Makarewicz, Stefan Hagel, Christina Bahrs, Aurelia Kimmig, Hans Proquitté, Joel Guerra, Dagmar Rimek, Bettina Löffler, Mathias W Pletz, and CoNAN Study Group.
• Institute for Infectious Diseases and Infection Control, Jena University Hospital - Friedrich Schiller University, Jena, Germany; Centre for Sepsis Control and Care (CSCC), Jena University Hospital - Friedrich Schiller University, Jena, Germany; Department of Anaesthesiology and Intensive Care, Jena University Hospital - Friedrich Schiller University, Jena, Germany. Electronic address: Sebastian.Weis@med.uni-jena.de.
• Clin. Microbiol. Infect. 2021 Mar 1; 27 (3): 470.e1-470.e9.

ObjectivesDue to a substantial proportion of asymptomatic and mild courses, many severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections remain unreported. Therefore, assessment of seroprevalence may detect the real burden of disease. We aimed to determine and characterize the rate of SARS-CoV-2 infections and the resulting seroprevalence in a defined population. The primary objective of the study was to assess SARS-CoV-2 antibody seroprevalence using six different IgG-detecting immunoassays. Secondary objectives of the study were: (a) to determine potential risk factors for symptomatic versus asymptomatic coronavirus disease 2019 courses, and (b) to investigate the rate of virus RNA-persistence.MethodsCoNAN is a population-based cohort study performed in the community Neustadt am Rennsteig, Germany, which was quarantined from 22 March to 5 April after six SARS-CoV-2 cases were detected in the village's population. The SARS-CoV-2 outbreak comprised 51 cases and 3 deaths. The CoNAN study was performed from 13 May to 22 May 2020, 6 weeks after a SARS-CoV-2 outbreak.ResultsWe enrolled a total of 626 participants (71% of the community population) for PCR and antibody testing in the study. All actual SARS-CoV-2 PCR tests were negative. Fifty-two out of 620 (8.4%) participants had antibodies against SARS-CoV-2 in at least two different assays. There were 38 participants with previously PCR-confirmed SARS-CoV-2 infection. Of those, only 19 (50%) displayed anti-SARS-CoV-2 antibodies. We also show that antibody-positive participants with symptoms compatible with a respiratory tract infection had significantly higher antibody levels then asymptomatic participants (EU-assay: median 2.9 versus 7.2 IgG-index, p 0.002; DS-assay: median 45.2 versus 143 AU/mL, p 0.002). Persisting viral replication was not detected.ConclusionsOur data question the relevance and reliability of IgG antibody testing to detect past SARS-CoV-2 infections 6 weeks after an outbreak. We conclude that assessing immunity for SARS-CoV-2 infection should not rely on antibody tests alone.Copyright © 2020 The Author(s). Published by Elsevier Ltd.. All rights reserved.

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