Lund University Publications

@article{1b988635-20dc-449c-96c7-08bb6852413b,
  abstract     = {{<p>BACKGROUND: The risk of SARS-CoV-2 infection among health care workers (HCWs) is a concern, but studies that conclusively determine whether HCWs are over-represented remain limited. Furthermore, methods used to confirm past infection vary and the immunological response after mild COVID-19 is still not well defined.</p><p>METHOD: 314 HCWs were recruited from a Swedish Infectious Diseases clinic caring for COVID-19 patients. IgG antibodies were measured using two commercial assays (Abbot Architect nucleocapsid (N)-assay and YHLO iFlash-1800 N and spike (S)-assays) at five time-points, from March 2020 to January 2021, covering two pandemic waves. Seroprevalence was assessed in matched blood donors at three time-points. More extensive analyses were performed in 190 HCWs in September/October 2020, including two additional IgG-assays (DiaSorin LiaisonXL S1/S2 and Abbot Architect receptor-binding domain (RBD)-assays), neutralizing antibodies (NAbs), and CD4 + T-cell reactivity using an in-house developed  in vitro whole-blood assay based on flow cytometric detection of activated cells after stimulation with Spike S1-subunit or Spike, Membrane and Nucleocapsid (SMN) overlapping peptide pools. </p><p>FINDINGS: Seroprevalence was higher among HCWs compared to sex and age-matched blood donors at all time-points. Seropositivity increased from 6.4% to 16.3% among HCWs between May 2020 and January 2021, compared to 3.6% to 11.9% among blood donors. We found significant correlations and high levels of agreement between NAbs and all four commercial IgG-assays. At 200-300 days post PCR-verified infection, there was a wide variation in sensitivity between the commercial IgG-assays, ranging from &lt;30% in the N-assay to &gt;90% in the RBD-assay. There was only moderate agreement between NAbs and CD4 + T-cell reactivity to S1 or SMN. Pre-existing CD4 + T-cell reactivity was present in similar proportions among HCW who subsequently became infected and those that did not. </p><p>CONCLUSIONS: HCWs in COVID-19 patient care in Sweden have been infected with SARS-CoV-2 at a higher rate compared to blood donors. We demonstrate substantial variation between different IgG-assays and propose that multiple serological targets should be used to verify past infection. Our data suggest that CD4 + T-cell reactivity is not a suitable measure of past infection and does not reliably indicate protection from infection in naive individuals. </p>}},
  author       = {{Marklund, Emelie and Leach, Susannah and Nyström, Kristina and Lundgren, Anna and Liljeqvist, Jan-Åke and Nilsson, Staffan and Yilmaz, Aylin and Andersson, Lars-Magnus and Bemark, Mats and Gisslén, Magnus}},
  issn         = {{1664-3224}},
  keywords     = {{Adult; Aged; Antibodies, Neutralizing/immunology; Antibodies, Viral/immunology; CD4-Positive T-Lymphocytes/immunology; COVID-19/immunology; Female; Follow-Up Studies; Health Personnel; Humans; Immunity/immunology; Immunoglobulin G/immunology; Male; Middle Aged; Pandemics/prevention & control; SARS-CoV-2/immunology; Seroepidemiologic Studies; Sweden; Young Adult}},
  language     = {{eng}},
  pages        = {{1--12}},
  publisher    = {{Frontiers Media S. A.}},
  series       = {{Frontiers in Immunology}},
  title        = {{Longitudinal Follow Up of Immune Responses to SARS-CoV-2 in Health Care Workers in Sweden With Several Different Commercial IgG-Assays, Measurement of Neutralizing Antibodies and CD4
        + T-Cell Responses.}},
  url          = {{http://dx.doi.org/10.3389/fimmu.2021.750448}},
  doi          = {{10.3389/fimmu.2021.750448}},
  volume       = {{12}},
  year         = {{2021}},
}