Seroprevalence of antibodies to SARS-CoV-2 in healthcare workers: a cross-sectional study

Ebinger, Joseph E; Botwin, Gregory J; Albert, Christine M; Alotaibi, Mona; Arditi, Moshe; Berg, Anders H; Binek, Aleksandra; Botting, Patrick; Fert-Bober, Justyna; Figueiredo, Jane C; Grein, Jonathan D; Hasan, Wohaib; Henglin, Mir; Hussain, Shehnaz K; Jain, Mohit; Joung, Sandy; Karin, Michael; Kim, Elizabeth H; Li, Dalin; Liu, Yunxian; Luong, Eric; McGovern, Dermot P B; Merchant, Akil; Merin, Noah; Miles, Peggy B; Minissian, Margo; Nguyen, Trevor Trung; Raedschelders, Koen; Rashid, Mohamad A; Riera, Celine E; Riggs, Richard V; Sharma, Sonia; Sternbach, Sarah; Sun, Nancy; Tourtellotte, Warren G; Van Eyk, Jennifer E; Sobhani, Kimia; Braun, Jonathan G; Cheng, Susan

OBJECTIVE: We sought to determine the extent of SARS-CoV-2 seroprevalence and the factors associated with seroprevalence across a diverse cohort of healthcare workers. DESIGN: Observational cohort study of healthcare workers, including SARS-CoV-2 serology testing and participant questionnaires. SETTINGS: A multisite healthcare delivery system located in Los Angeles County. PARTICIPANTS: A diverse and unselected population of adults (n=6062) employed in a multisite healthcare delivery system located in Los Angeles County, including individuals with direct patient contact and others with non-patient-oriented work functions. MAIN OUTCOMES: Using Bayesian and multivariate analyses, we estimated seroprevalence and factors associated with seropositivity and antibody levels, 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 (OR 11.04, p<0.001) in addition to fever (OR 2.02, p=0.002) and myalgias (OR 1.65, p=0.035). After adjusting for potential confounders, seroprevalence was also associated with Hispanic ethnicity (OR 1.98, p=0.001) and African-American race (OR 2.02, p=0.027) as well as contact with a COVID-19-diagnosed individual in the household (OR 5.73, p<0.001) or clinical work setting (OR 1.76, p=0.002). 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 societal factors. 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 modelling 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.