LAUSR

To the Editor—To better understand the effectiveness of occupational infection control measures during the coronavirus disease 2019 (COVID-19) pandemic, we surveyed and antibody tested employees of Bassett Healthcare Network, located in rural upstate New York, 200 miles northwest of New York City. Employer-sponsored SARS-CoV-2 IgG antibody testing was conducted from May 4 to 29, 2020. Network leadership prioritized employees with a high likelihood of exposure to COVID-19–infected patients. A 21.7% random sample of employees was also included for antibody testing to ensure that our seroprevalence estimate was representative of all network employees. The study questionnaire captured demographics, COVID-19 polymerase chain reaction (PCR) status, potential COVID-19 work and nonwork exposures, and COVID-19 symptoms experienced since January 1, 2020 (based on the Centers for Disease Control and Prevention’s case report form). The recall period for exposure questions (March 1–May 31, 2020) coincided with New York State’s stay-at-home order plus 2 weeks. We compared seroprevalence among employees to that for patients tested during the same period. Employee serology testing was performed by Bassett Medical Center Laboratory using the SARS-CoV-2 IgG Abbott Architect assay (Abbott Laboratories, Abbott Park, IL), with 100% sensitivity and 99.6% specificity.1 IgG level ≥1.40 was defined as positive. Most serology testing for patients (96%) was conducted by the Mayo Clinic using the VITROS Anti-SARS-CoV-2 IgG Test (Ortho-Clinical Diagnostics, Linden, NJ), with 90.0% sensitivity and 100% specificity.2 The remaining patient tests were conducted by the in-house laboratory using the Abbott test. We compared questionnaire responses by antibody status using χ2 tests for categorical variables and t tests for continuous variables. Analyses were conducted using SAS version 9.3 software (SAS Institute, Cary, NC). This study was approved by the Mary Imogene Bassett Institutional Review Board. Results