Background: The COVID-19 pandemic has disproportionately affected workers in certain industries and occupations, and the workplace can be a high risk setting for SARS-CoV-2 transmission. In this study, we measured SARS-CoV-2 antibody prevalence and identified work-related risk factors in a population primarily working at industrial livestock operations. Methods: We used a multiplex salivary SARS-CoV-2 IgG antibody assay to determine infection-induced antibody prevalence among 236 adult (>=18 years) North Carolina residents between February 2021 and August 2022. We used the National Institute for Occupational Safety and Health Industry and Occupation Computerized Coding System (NIOCCS) to classify employed participants' industry and compared infection-induced IgG prevalence by participant industry and with the North Carolina general population. We also combined antibody results with reported SARS-CoV-2 molecular test positivity and vaccination history to identify evidence of prior infection. We used logistic regression to estimate odds ratios of prior infection by potential work-related risk factors, adjusting for industry and date. Results: Most participants (55%) were infection-induced IgG positive, including 71% of animal slaughtering and processing industry workers, which is 1.5 to 4.3 times higher compared to the North Carolina general population, as well as higher than molecularly-confirmed cases and the only other serology study we identified of animal slaughtering and processing workers. Considering questionnaire results in addition to antibodies, the proportion of participants with evidence of prior infection increased slightly, to 61%, including 75% of animal slaughtering and processing workers. Participants with more than 1000 compared to 10 or fewer coworkers at their jobsite had higher odds of prior infection (adjusted odds ratio [aOR] 4.5, 95% confidence interval [CI] 1.0 to 21.0). Conclusions: This study contributes evidence of the severe and disproportionate impacts of COVID-19 on animal processing and essential workers and workers in large congregate settings. We also demonstrate the utility of combining non-invasive biomarker and questionnaire data for the study of workplace exposures.

The authors have declared no competing interest.

This study was supported by an anonymous gift, the JHU COVID-19 Research and Response Program, the FIA Foundation, NIAID R21 AI139784, and a NIOSH POE Total Worker Health Center (U19 OH012297) pilot project grant. C.G., K. Koehler, and C.D.H. were supported by NIOSH ERC (T42 OH0008428). M.F.D and K. Koehler were also supported by the NIOSH POE Center (U19 OH012297). N.P., K. Kruczynski, M.G.R., K.S., and C.D.H. were supported by an anonymous gift, the JHU COVID-19 Research and Response Program, and the FIA Foundation. C.D.H was additionally supported by NIEHS (R01ES026973), NIAID (R43AI141265, R01AI130066, R01ES026973), and NIH (U24OD023382).

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The Institutional Review Board (IRB) of the Johns Hopkins Bloomberg School of Public Health gave ethical approval for this study (IRB00014420).

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