SARS-CoV-2 Seroprevalence Across a Diverse Cohort of Healthcare Workers
Authors: 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 
Published: August 2020

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.

Key Points

Question

What is the SARS-CoV-2 IgG seroprevalence rate across a large and diverse healthcare worker population, and which clinical, envionrmental, and symptom-based measures are associated with seropositivity?

Findings

We observed a seroprevalence rate of 4.1%. Adjusting for potential confounders, seropositivity was associated with younger age, Hispanic ethnicity, African-American race, and the symptom of anosmia, while not significantly associated with any pre-existing medical conditions.

Meaning

Factors associated with SARS-CoV-2 seroprevalence among our healthcare workers underscore the importance of exposure sources beyond the workplace.