Seroprevalence of SARS-CoV-2 antibodies and reduced risk of reinfection through 6 months: a Danish observational cohort study of 44 000 healthcare workers

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DOI

  • Kasper Iversen, Københavns Universitet
  • ,
  • Jonas Henrik Kristensen, Københavns Universitet
  • ,
  • Rasmus Bo Hasselbalch, Københavns Universitet
  • ,
  • Mia Pries-Heje, Københavns Universitet
  • ,
  • Pernille Brok Nielsen, Københavns Universitet
  • ,
  • Andreas Dehlbæk Knudsen, Københavns Universitet
  • ,
  • Kamille Fogh, Københavns Universitet
  • ,
  • Jakob Boesgaard Norsk, Københavns Universitet
  • ,
  • Ove Andersen, Københavns Universitet
  • ,
  • Thea Køhler Fischer, Københavns Universitet
  • ,
  • Claus Antonio Juul Jensen, Københavns Universitet
  • ,
  • Christian Torp-Pedersen, Københavns Universitet
  • ,
  • Jørgen Rungby
  • Sisse Bolm Ditlev, Københavns Universitet
  • ,
  • Ida Hageman, Københavns Universitet, Mental Health Services—The Capital Region of Denmark
  • ,
  • Rasmus Møgelvang, Københavns Universitet
  • ,
  • Mikkel Gybel-Brask, Københavns Universitet
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  • Ram B. Dessau, Sjællands Universitetshospital, Syddansk Universitet
  • ,
  • Erik Sørensen, Københavns Universitet
  • ,
  • Lene Harritshøj, Københavns Universitet
  • ,
  • Fredrik Folke, Københavns Universitet
  • ,
  • Curt Sten, Københavns Universitet
  • ,
  • Maria Elizabeth Engel Møller, Københavns Universitet
  • ,
  • Thomas Benfield, Københavns Universitet
  • ,
  • Henrik Ullum, Statens Serum Institut
  • ,
  • Charlotte Sværke Jørgensen, Statens Serum Institut
  • ,
  • Christian Erikstrup
  • Sisse R. Ostrowski, Københavns Universitet
  • ,
  • Susanne Dam Nielsen
  • Henning Bundgaard, Københavns Universitet

Objectives: Antibodies to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) are a key factor in protecting against coronavirus disease 2019 (COVID-19). We examined longitudinal changes in seroprevalence in healthcare workers (HCWs) in Copenhagen and the protective effect of antibodies against SARS-CoV-2. Methods: In this prospective study, screening for antibodies against SARS-CoV-2 (ELISA) was offered to HCWs three times over 6 months. HCW characteristics were obtained by questionnaires. The study was registered at ClinicalTrials.gov, NCT04346186. Results: From April to October 2020 we screened 44 698 HCWs, of whom 2811 were seropositive at least once. The seroprevalence increased from 4.0% (1501/37 452) to 7.4% (2022/27 457) during the period (p < 0.001) and was significantly higher than in non-HCWs. Frontline HCWs had a significantly increased risk of seropositivity compared to non-frontline HCWs, with risk ratios (RRs) at the three rounds of 1.49 (95%CI 1.34–1.65, p < 0.001), 1.52 (1.39–1.68, p < 0.001) and 1.50 (1.38–1.64, p < 0.001). The seroprevalence was 1.42- to 2.25-fold higher (p < 0.001) in HCWs from dedicated COVID-19 wards than in other frontline HCWs. Seropositive HCWs had an RR of 0.35 (0.15–0.85, p 0.012) of reinfection during the following 6 months, and 2115 out of 2248 (95%) of those who were seropositive during rounds one or two remained seropositive after 4–6 months. The 133 of 2248 participants (5.0%) who seroreverted were slightly older and reported fewer symptoms than other seropositive participants. Conclusions: HCWs remained at increased risk of infection with SARS-CoV-2 during the 6-month period. Seropositivity against SARS-CoV-2 persisted for at least 6 months in the vast majority of HCWs and was associated with a significantly lower risk of reinfection.

OriginalsprogEngelsk
TidsskriftClinical Microbiology and Infection
Vol/bind28
Nummer5
Sider (fra-til)710-717
Antal sider8
ISSN1198-743X
DOI
StatusUdgivet - maj 2022

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