SARS-CoV-2 antibody prevalence among industrial livestock operation workers and nearby community residents, North Carolina, USA, 2021-2022

Abstract

ABSTRACTIndustrial livestock operations (ILOs), particularly processing facilities, emerged as centers of coronavirus disease 2019 (COVID-19) outbreaks in spring 2020. Confirmed cases of COVID-19 underestimate true prevalence. To investigate prevalence of antibodies against SARS-CoV-2, we enrolled 279 participants in North Carolina from February 2021 to July 2022: 90 from households with at least one ILO worker (ILO), 97 from high-ILO intensity areas (ILO neighbors – ILON), and 92 from metropolitan areas (Metro). Participants provided a saliva swab we analyzed for SARS-CoV-2 IgG using a multiplex immunoassay. Prevalence of infection-induced IgG (positive for nucleocapsid and receptor binding domain) was higher among ILO (63%) compared to ILON (42.9%) and Metro (48.7%) participants (prevalence ratio [PR] =1.38; 95% confidence interval [CI]: 1.06, 1.80; ref. ILON and Metro combined). Prevalence of infection-induced IgG was also higher among ILO participants compared to an Atlanta healthcare worker cohort (PR=2.45, 95% CI: 1.8, 3.3) and a general population cohort in North Carolina (PRs 6.37-10.67). Infection-induced IgG prevalence increased over the study period. Participants reporting not masking in public in the past two weeks had higher infection-induced IgG prevalence (78.6%) compared to participants reporting masking (49.3%) (PR=1.59; 95% CI: 1.19, 2.13). Lower education, more people per bedroom, Hispanic/Latino ethnicity, and more contact with people outside the home were also associated with higher infection-induced IgG prevalence. Similar proportions of ILO (51.6%), ILON (48.4%), and Metro (55.4%) participants completed the COVID-19 primary vaccination series; median completion was more than four months later for ILO compared to ILON and Metro participants.ImportanceFew studies have measured COVID-19 seroprevalence in North Carolina, especially among rural, Black, and Hispanic/Latino communities that have been heavily affected. Antibody results show high rates of COVID-19 among industrial livestock operation workers and their household members. Antibody results add to evidence of health disparities in COVID-19 by socioeconomic status and ethnicity. Associations between masking and physical distancing with antibody results also add to evidence of the effectiveness of these prevention strategies. Delays in the timing of receipt of COVID-19 vaccination reinforce the importance of dismantling vaccination barriers, especially for industrial livestock operation workers and their household members.