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

<jats:sec><jats:title>Objective</jats:title><jats:p>We sought to determine the extent of SARS-CoV-2 seroprevalence and the factors associated with seroprevalence across a diverse cohort of healthcare workers.</jats:p></jats:sec><jats:sec><jats:title>Design</jats:title><jats:p>Observational cohort study of healthcare workers, including SARS-CoV-2 serology testing and participant questionnaires.</jats:p></jats:sec><jats:sec><jats:title>Settings</jats:title><jats:p>A multisite healthcare delivery system located in Los Angeles County.</jats:p></jats:sec><jats:sec><jats:title>Participants</jats:title><jats:p>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.</jats:p></jats:sec><jats:sec><jats:title>Main outcomes</jats:title><jats:p>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.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>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.</jats:p></jats:sec><jats:sec><jats:title>Conclusion and relevance</jats:title><jats:p>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.</jats:p></jats:sec>