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

• Published in: The Journal of infectious diseases Vol. 223; no. 4; pp. 589 - 599
• Main Authors: Trieu, Mai-Chi, Bansal, Amit, Madsen, Anders, Zhou, Fan, Sævik, Marianne, Vahokoski, Juha, Brokstad, Karl Albert, Krammer, Florian, Tøndel, Camilla, Mohn, Kristin G I, Blomberg, Bjørn, Langeland, Nina, Cox, Rebecca J
• Format: Journal Article
• Language: English
• Published: US Oxford University Press 24.02.2021
• Subjects: Adult; Aged; Antibodies; Antibodies, Neutralizing - blood; Antibodies, Viral - blood; Asymptomatic Infections; Cohort analysis; Coronaviruses; COVID-19; COVID-19 - immunology; Female; Health care; Health Personnel - statistics & numerical data; Humans; Immunoglobulin A; Immunoglobulin G; Immunoglobulin M; Major and Brief Reports; Male; Medical personnel; Middle Aged; Norway; Pandemics; Patients; Polymerase chain reaction; Prospective Studies; RNA-directed DNA polymerase; SARS-CoV-2 - immunology; Seroconversion; Severe acute respiratory syndrome coronavirus 2; Spike Glycoprotein, Coronavirus - immunology; Young Adult; Norway; COVID-19; SARS-CoV-2; IgA; seroconversion; spike protein; IgG; neutralizing antibody; health care workers; antibody characterization; IgM
• ISSN: 0022-1899; 1537-6613
• DOI: 10.1093/infdis/jiaa737

Abstract 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. Low numbers of SARS-CoV-2–seropositive HCW were found in Norway and 1.8% of HCW seroconverted with neutralizing antibodies. Seropositivity was higher than RT-PCR positivity in HCW with 36% asymptomatic, representing a risk of infection within the health care setting.