SARS-CoV-2-Specific Neutralizing Antibody Responses in Norwegian Health Care Workers after the First Wave of COVID-19 Pandemic: A Prospective Cohort Study

Mai Chi Trieu, Amit Bansal, Anders Madsen, Fan Zhou, Marianne Sævik, Juha Vahokoski, Karl Albert Brokstad, Florian Krammer, Camilla Tøndel, Kristin G.I. Mohn, Bjørn Blomberg, Nina Langeland, Rebecca J. Cox, Bård Kittang, Dagrunn Waag Linchausen, Håkon Amdam, Therese Bredholt Onyango, Geir Bredholt, Nina Ertesvåg, Sarah LarteyHelene Heitmann Sandnes, Fredrik Grøvan, Hauke Bartsch, Heidi Syre, Francisco Real, Åse Garløv Berg

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


Background: During the coronavirus disease 2019 (COVID-19) pandemic, many countries experienced infection in health care workers (HCW) due to overburdened health care systems. Whether infected HCW acquire protective immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is unclear. Methods: In a Norwegian prospective cohort study, we enrolled 607 HCW before and after the first COVID-19 wave. Exposure history, COVID-19-like symptoms, and serum samples were collected. SARS-CoV-2-specific antibodies were characterized by spike-protein IgG/IgM/IgA enzyme-linked immunosorbent and live-virus neutralization assays. Results: Spike-specific IgG/IgM/IgA antibodies increased after the first wave in HCW with, but not in HCW without, COVID-19 patient exposure. Thirty-two HCW (5.3%) had spike-specific antibodies (11 seroconverted with ≥4-fold increase, 21 were seropositive at baseline). Neutralizing antibodies were found in 11 HCW that seroconverted, of whom 4 (36.4%) were asymptomatic. Ninety-seven HCW were tested by reverse transcriptase polymerase chain reaction (RT-PCR) during follow-up; 8 were positive (7 seroconverted, 1 had undetectable antibodies). Conclusions: We found increases in SARS-CoV-2 neutralizing antibodies in infected HCW, especially after COVID-19 patient exposure. Our data show a low number of SARS-CoV-2-seropositive HCW in a low-prevalence setting; however, the proportion of seropositivity was higher than RT-PCR positivity, highlighting the importance of antibody testing.

Original languageEnglish
Pages (from-to)589-599
Number of pages11
JournalJournal of Infectious Diseases
Issue number4
StatePublished - 15 Feb 2021


  • COVID-19
  • IgA
  • IgG
  • IgM
  • SARS-CoV-2
  • antibody characterization
  • health care workers
  • neutralizing antibody
  • seroconversion
  • spike protein


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