Serologic Surveillance and Phylogenetic Analysis of SARS-CoV-2 Infection Among Hospital Health Care Workers
Authors: Jonne J. Sikkens, David T. P. Buis, Edgar J. G. Peters, Mireille Dekker, Michiel Schinkel, Tom D. Y. Reijnders, Alex. R. Schuurman, Justin de Brabander, A. H. Ayesha Lavell, Jaap J. Maas, Jelle Koopsen, Alvin X. Han, Colin A. Russell, Janke Schinkel, Marcel Jonges, Sébastien Matamoros, Suzanne Jurriaans, Rosa van Mansfeld, W. Joost Wiersinga, Yvo M. Smulders, Menno D. de Jong, Marije K. Bomers
Journal: JAMA Network Open (2021)

<h3>Importance</h3> It is unclear when, where, and by whom health care workers (HCWs) working in hospitals are infected with SARS-CoV-2. <h3>Objective</h3> To determine how often and in what manner nosocomial SARS-CoV-2 infection occurs in HCW groups with varying exposure to patients with COVID-19. <h3>Design, Setting, and Participants</h3> This cohort study comprised 4 weekly measurements of SARS-CoV-2–specific antibodies and collection of questionnaires from March 23 to June 25, 2020, combined with phylogenetic and epidemiologic transmission analyses at 2 university hospitals in the Netherlands. Included individuals were HCWs working in patient care for those with COVID-19, HCWs working in patient care for those without COVID-19, and HCWs not working in patient care. Data were analyzed from August through December 2020. <h3>Exposures</h3> Varying work-related exposure to patients infected with SARS-CoV-2. <h3>Main Outcomes and Measures</h3> The cumulative incidence of and time to SARS-CoV-2 infection, defined as the presence of SARS-CoV-2–specific antibodies in blood samples, were measured. <h3>Results</h3> Among 801 HCWs, there were 439 HCWs working in patient care for those with COVID-19, 164 HCWs working in patient care for those without COVID-19, and 198 HCWs not working in patient care. There were 580 (72.4%) women, and the median (interquartile range) age was 36 (29-50) years. The incidence of SARS-CoV-2 was increased among HCWs working in patient care for those with COVID-19 (54 HCWs [13.2%; 95% CI, 9.9%-16.4%]) compared with HCWs working in patient care for those without COVID-19 (11 HCWs [6.7%; 95% CI, 2.8%-10.5%]; hazard ratio [HR], 2.25; 95% CI, 1.17-4.30) and HCWs not working in patient care (7 HCWs [3.6%; 95% CI, 0.9%-6.1%]; HR, 3.92; 95% CI, 1.79-8.62). Among HCWs caring for patients with COVID-19, SARS-CoV-2 cumulative incidence was increased among HCWs working on COVID-19 wards (32 of 134 HCWs [25.7%; 95% CI, 17.6%-33.1%]) compared with HCWs working on intensive care units (13 of 186 HCWs [7.1%; 95% CI, 3.3%-10.7%]; HR, 3.64; 95% CI, 1.91-6.94), and HCWs working in emergency departments (7 of 102 HCWs [8.0%; 95% CI, 2.5%-13.1%]; HR, 3.29; 95% CI, 1.52-7.14). Epidemiologic data combined with phylogenetic analyses on COVID-19 wards identified 3 potential HCW-to-HCW transmission clusters. No patient-to-HCW transmission clusters could be identified in transmission analyses. <h3>Conclusions and Relevance</h3> This study found that HCWs working on COVID-19 wards were at increased risk for nosocomial SARS-CoV-2 infection with an important role for HCW-to-HCW transmission. These findings suggest that infection among HCWs deserves more consideration in infection prevention practice.