Figure 1.

Screening for SARS-CoV-2 RBD-specific antibodies in HCW before and after COVID-19 patient admissions. A, HCW (n = 607) were recruited between 6 March 2020 and 9 April 2020, and followed up after 6–10 weeks. Each circle represents 1 HCW and their anti-RBD antibodies measured in the screening ELISA as OD at 450/620 nm (left y-axis). The numbers of hospitalized COVID-19 patients (blue line) and cumulative deaths (orange line) in Bergen, Norway are plotted on the right y-axis. Lockdown was initiated in Norway on 12 March 2020 and a gradual reopening starting on 20 April 2020. B, HCW were grouped into high risk (testing facility, COVID-19–designated wards, and intensive care unit wards) and low risk (no known exposure to COVID-19 patients) of occupational exposure to SARS-CoV-2 according to their working department and information in their case report forms. Dotted lines are cutoffs for negative screening results (OD < 0.430) and positive screening results (OD ≥ 0.708) (see Supplementary Figure 1 for further information). Horizontal lines represent mean with standard deviation. OD values were log-transformed and compared between time points in mixed-effects models with adjustment for subject variation, age, sex, and other relevant demographic factors. *P < .05. Abbreviations: COVID-19, coronavirus disease 2019; ELISA, enzyme-linked immunosorbent assay; HCW, health care workers; OD, optical density; RBD, receptor-binding domain; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.