SARS-CoV-2 Seroprevalence Across a Diverse Cohort of Healthcare Workers

Ebinger, J.; Botwin, G. J.; Albert, C. M.; Alotaibi, M.; Arditi, M.; Berg, A. H.; Binek, A.; Botting, P. G.; Fert-Bober, J.; Figueiredo, J. C.; Grein, J. D.; Hasan, W.; Henglin, M.; Hussain, S. K.; Jain, M.; Joung, S.; Karin, M.; Kim, E. H.; Li, D.; Liu, Y.; Luong, E.; McGovern, D. P. B.; Merchant, A.; Merin, N. M.; Miles, P. B.; Minissian, M.; Nguyen, T.-T.; Raedschelders, K.; Rashid, M. A.; Riera, C. E.; Riggs, R. V.; Sharma, S.; Sternbach, S.; Sun, N.; Tourtellotte, W. G.; Van Eyk, J. E.; Sobhani, K.; Braun, J. G.; Cheng, S.

Importance: Antibody testing is important for understanding patterns of exposure and potential immunity to SARS-CoV-2. Prior data on seroprevalence have been subject to variations in selection of individuals and nature as well as timing of testing in relation to exposures. Objective: We sought to determine the extent of SARS-CoV-2 seroprevalance and the factors associated with seroprevelance across a diverse cohort of healthcare workers. Design: Observational cohort study of healthcare workers, including SARS-CoV-2 serology testing and participant questionaires. Participants: A diverse and unselected population of adults (n=6,062) employed in a multi-site healthcare delivery system located in Los Angeles County, including individuals with direct patient contact and others with non-patient-oriented work functions. Exposure: Exposure and infection with the SARS-CoV-2 virus, as determined by seropositivity. Main Outcomes: Using Bayesian and multi-variate analyses, we estimated seroprevalence and factors associated with seropositivity and antibody titers, including pre-existing demographic and clinical characteristics; potential Covid-19 illness related exposures; and, symptoms consistent with Covid-19 infection. Results: We observed a seroprevalence rate of 4.1%, with anosmia as the most prominently associated self-reported symptom in addition to fever, dry cough, anorexia, and myalgias. After adjusting for potential confounders, pre-existing medical conditions were not associated with antibody positivity. However, seroprevalence was associated with younger age, Hispanic ethnicity, and African-American race, as well as presence of either a personal or household member having a prior diagnosis of Covid-19. Importantly, African American race and Hispanic ethnicity were associated with antibody positivity even after adjusting for personal Covid-19 diagnosis status, suggesting the contribution of unmeasured structural or societally factors. Notably, number of people, or children, in the home was not associated with antibody positivity. Conclusion and Relevance: The demographic factors associated with SARS-CoV-2 seroprevalence among our healthcare workers underscore the importance of exposure sources beyond the workplace. The size and diversity of our study population, combined with robust survey and modeling techniques, provide a vibrant picture of the demographic factors, exposures, and symptoms that can identify individuals with susceptibility as well as potential to mount an immune response to Covid-19.