Comparison of the Prevalence of SARS-CoV-2 Nucleoprotein Antibodies in Healthcare Workers and an Unselected Adult and Pediatric All-Comer Patient Population in Austria

Background: Serosurveys are critical to determine prior exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and enable population-level surveillance. Only limited data on the change in SARS-CoV-2 exposure over time and direct comparisons between adult and pediatric patients and healthcare workers are available.Methods: A longitudinal study enrolling healthcare professionals and concurrent serial cross-sectional studies of unselected all-comer patients were conducted at an Austrian academic medical center. Healthcare workers were tested at enrollment and after 1, 2, 3, 6, and 12 months. The cross-sectional studies in patients were conducted at 3 time periods, which roughly coincided with the times after the first, second, and third wave of SARS-CoV-2 in Austria (i.e., August 24 - September 7, 2020; February 8 - 22, 2021, and November 9 - 23, 2021). Antibodies against the SARS-CoV-2 nucleoprotein antigen were measured using a sandwich electrochemiluminescence assay (Roche). We estimated the seroprevalence and 95% confidence intervals (CI) according to the Wilson score method. Findings: In total, 2,735 and 9,275 samples were measured in 812 healthcare workers (median age 40 years, 78% female) and 8,451patients (median age 55 years, 52% female), respectively. Over the entire study period, antibodies against SARS-CoV-2 were detected in 98 of 812 healthcare workers, resulting in a seroprevalence of 12·1% (95% CI 10·0% to 14·5%), which did not differ significantly (P=0·63) from that of the all-comer patient population at the end of the study period (407/3184; 12·8%, 95% CI 11·7% to 14·0%). The seroprevalence between healthcare workers and patients did not differ significantly at any time and was 1·5 to 2-fold higher than the number of confirmed cases in Austria throughout the pandemic. In particular, there was no significant difference in the seroprevalence between pediatric and adult patients at any of the tested time periods. Interpretation: Throughout the pandemic, healthcare staff and an adult and pediatric all-comer patient population had similar exposure to SARS-CoV-2. These findings suggest that the established hospital containment policies were effective.Funding: This study was funded by the Austrian Science Fund (KLI 876-B).Declaration of Interest: MR, CN, CJB, ESS, TS, FJ, EA, FH, HH, TP, and CH report no conflicts of interest for this work. Outside of the submitted work, CJB reports honoraria for serving on advisory boards and speaker honoraria from Amgen, Daiichi-Sankyo, Novartis, SOBI; board member of Technoclone. ESS reports research grants from the US National Health Institutes (NIH), the European Commission’s Program Horizon 2020, the Austrian Science Funds (FWF), and the Austrian Research Promotion Agency (FFG). HH reports grants from Glock Health Science and Research, BlueSky Immunotherapies and the Austrian Ministry of Education Science and Research. TAZ reports research grants from the Austrian Science Funds and the German Research Foundation, honoraria for serving on advisory boards from Boehringer Ingelheim, personal fees from Alkem Metabolics, AstraZeneca, Boehringer Ingelheim, and Sun Pharmaceutical Industries, and educational grants from Eli Lilly and Company.Ethical Approval: The study was conducted after approval from the institutional review board of the Medical University of Vienna (EK 1387/2020)