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DOI: 10.1055/a-2497-6449
Original Article

Piloting of a surveillance system for acute respiratory diseases: COVID-19 monitoring using Sick Leave Certificates

Article in several languages: English | deutsch

Authors

  • Inga Overesch

    1   Infektionsepidemiologie und -surveillance, Niedersächsisches Landesgesundheitsamt, Hannover, Germany

  • Ulrike Junius-Walker

    2   Gesundheitsmonitoring und Prävention, Niedersächsisches Landesgesundheitsamt, Hannover, Germany

  • Johanna Schneider

    1   Infektionsepidemiologie und -surveillance, Niedersächsisches Landesgesundheitsamt, Hannover, Germany

  • Mareike Wollenweber

    1   Infektionsepidemiologie und -surveillance, Niedersächsisches Landesgesundheitsamt, Hannover, Germany

  • Karina Usipbekova

    1   Infektionsepidemiologie und -surveillance, Niedersächsisches Landesgesundheitsamt, Hannover, Germany

  • Wiebke Böhne

    3   Politik Forschung und Presse, AOK Niedersachsen, Die Gesundheitskasse, Hannover, Germany

  • Ina Holle

    1   Infektionsepidemiologie und -surveillance, Niedersächsisches Landesgesundheitsamt, Hannover, Germany

  • Johannes Dreesman

    1   Infektionsepidemiologie und -surveillance, Niedersächsisches Landesgesundheitsamt, Hannover, Germany

  • Elke Mertens

    1   Infektionsepidemiologie und -surveillance, Niedersächsisches Landesgesundheitsamt, Hannover, Germany

  • Sveja Eberhard

    3   Politik Forschung und Presse, AOK Niedersachsen, Die Gesundheitskasse, Hannover, Germany
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Abstract

Introduction

With the end of the COVID-19 pandemic and the decreasing significance of official reporting figures, the Lower Saxony State Health Office developed and tested a new indicator: the "7-day sick leave incidence". Unlike previous surveillance indicators, it is intended for syndromic surveillance of COVID-19. This article explains the methodological development as well as its benefits, possible applications, and limitations.

Methods

The indicator is based on the weekly number of sick leaves due to COVID-19 per 100,000 health insurance members entitled to sickness benefits (KGbM) of the AOK Lower Saxony (AOKN). The development of the indicator involved differentiating between initial and follow-up sick leaves, investigating fluctuations in the number of KGbM, analysing the doctors’ assignments of ICD Codes U07.1! and U07.2!, and ensuring the timely availability of sick leave data.

Results

Initial and follow-up sick leaves were distinguished using a temporal algorithm. In 2022 and 2023, on average, 83.0% (s=5.4%) and 88.9% (s=2.3%) of all initial COVID-19-related sick notes were submitted on time by the end of the respective calendar week. Four out of 5 initial sick notes contained the doctors’ ICD code U07.1! (lab-confirmed COVID-19). The number of KGbM proved to be stable (M=1.218.202, s=11.003). When comparing the new “7-day sick leave incidence” with the officially used “7-day incidence rates” during pandemic, trends were highly similar in 2022 (r=0.89), but diverged significantly in 2023 (r=0.26) due to declining diagnostic activities for the “7-day incidence rates”.

Conclusion

The new 7-day-sick-leave incidence is a good representation of the post-pandemic COVID-19 infection dynamics. The indicator uses routine data and is easy to establish. Limitations relate to possible changes in diagnostic procedures, doctors’ coding behaviors and changing demands for sick leave.

Keywords

Covid-19 - Epidemiology - Syndromic surveillance - Secondary data analysis - Public reporting of healthcare data


Publication History

Received: 16 August 2024

Accepted: 05 December 2024

Accepted Manuscript online:
06 December 2024

Article published online:
02 October 2025

© 2025. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/).

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