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Risk Factors Associated With SARS-CoV-2 Infection Among Farmworkers in Monterey County, California

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To identify the key insights or developments described in this article
1 Credit CME
Key Points

Question  What are the risk factors associated with SARS-CoV-2 infection among farmworkers in California?

Findings  In this cross-sectional study of 1107 farmworkers, both household and workplace risk factors, including living with children aged 5 years or younger or unrelated roommates and living or working with an individual with known or suspected COVID-19, were associated with positive results on transcription-mediated amplification tests and immunoglobulin G tests for SARS-CoV-2 infection.

Meaning  These findings suggest that urgent distribution of vaccines to farmworkers and intervention on modifiable risk factors for SARS-CoV-2 infection are warranted given this population’s increased risk and the essential nature of their work.


Importance  Essential workers in agriculture and food production have been severely affected by the ongoing COVID-19 pandemic.

Objective  To identify risk factors associated with SARS-CoV-2 infection among farmworkers in California.

Design, Setting, and Participants  This cross-sectional study invited farmworkers in California’s Salinas Valley (Monterey County) receiving transcription-mediated amplification (TMA) tests for SARS-CoV-2 infection at federally qualified community clinics and community sites to participate. Individuals were eligible if they were not pregnant, were 18 years or older, had conducted farmwork since the pandemic started, and were proficient in English or Spanish. Survey data were collected and SARS-CoV-2 tests were conducted among participants from July 16 to November 30, 2020.

Exposures  Sociodemographic, household, community, and workplace characteristics.

Main Outcomes and Measures  TMA- and immunoglobulin G (IgG)–positive SARS-CoV-2 infection.

Results  A total of 1107 farmworkers (581 [52.5%] women; mean [SD] age, 39.7 [12.6] years) were included in these analyses. Most participants were born in Mexico (922 [83.3%]), were married or living with a partner (697 [63.0%]), and worked in the fields (825 [74.5%]). Overall, 118 of 911 (13.0%) had a positive result on their TMA test for SARS-CoV-2 infection, whereas 201 of 1058 (19.0%) had antibody evidence of infection. In multivariable analyses accounting for recruitment venue and enrollment period, the incidence of TMA-positive SARS-CoV-2 infection was higher among those with lower than primary school–level education (adjusted relative risk [aRR], 1.32; 95% CI, 0.99-1.76; non–statistically significant finding), who spoke an Indigenous language at home (aRR, 1.30; 95% CI, 0.97-1.73; non–statistically significant finding), who worked in the fields (aRR, 1.60; 95% CI, 1.03-2.50), and who were exposed to a known or suspected COVID-19 case at home (aRR, 2.98; 95% CI, 2.06-4.32) or in the workplace (aRR, 1.59; 95% CI, 1.18-2.14). Positive results on IgG tests for SARS-CoV-2 infection were more common among those who lived in crowded housing (aRR, 1.23; 95% CI, 0.98-1.53; non–statistically significant finding), with children aged 5 years or younger (aRR, 1.40; 95% CI, 1.11-1.76), with unrelated roommates (aRR, 1.40; 95% CI, 1.19-1.64), and with an individual with known or suspected COVID-19 (aRR, 1.59; 95% CI, 1.13-2.24). The risk of IgG positivity was also higher among those with body mass index of 30 or greater (aRR, 1.65; 95% CI, 1.01-2.70) or diabetes (aRR, 1.31; 95% CI, 0.98-1.75; non–statistically significant finding).

Conclusions and Relevance  In this cross-sectional study of farmworkers in California, both residential and workplace exposures were associated with SARS-CoV-2 infection. Urgent distribution of COVID-19 vaccines and intervention on modifiable risk factors are warranted given this population’s increased risk of infection and the essential nature of their work.

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Article Information

Accepted for Publication: July 6, 2021.

Published: September 15, 2021. doi:10.1001/jamanetworkopen.2021.24116

Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2021 Mora AM et al. JAMA Network Open.

Corresponding Author: Ana M. Mora, MD, PhD, Center for Environmental Research and Children’s Health, School of Public Health, University of California, Berkeley, 1995 University Ave, Ste 265, Berkeley, CA 94720 (animora@berkeley.edu).

Author Contributions: Drs Mora and Lewnard had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Drs Mora and Lewnard contributed equally to the work. Dr Eskenazi was co–principal investigator with Drs Mora and Lewnard.

Concept and design: Mora, Lewnard, Kogut, Chang, Jewell, Eskenazi.

Acquisition, analysis, or interpretation of data: Mora, Lewnard, Kogut, Rauch, Hernandez, Wong, Huen, Jewell, Holland, Harris, Cuevas, Eskenazi.

Drafting of the manuscript: Mora, Rauch, Chang, Jewell, Eskenazi.

Critical revision of the manuscript for important intellectual content: Mora, Lewnard, Kogut, Hernandez, Wong, Huen, Jewell, Holland, Harris, Cuevas, Eskenazi.

Statistical analysis: Mora, Lewnard, Rauch, Jewell, Eskenazi.

Obtained funding: Mora, Lewnard, Cuevas, Eskenazi.

Administrative, technical, or material support: Mora, Kogut, Hernandez, Huen, Chang, Holland, Harris, Cuevas, Eskenazi.

Supervision: Mora, Lewnard, Kogut, Hernandez, Wong, Holland, Harris, Cuevas, Eskenazi.

Conflict of Interest Disclosures: Dr Lewnard reported receiving grants from Pfizer outside the submitted work. No other disclosures were reported.

Funding/Support: This work was supported by the Innovative Genomics Institute and Clinica de Salud del Valle de Salinas.

Role of the Funder/Sponsor: The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

CHAMACOS-Project-19 Study Team Members: See Supplement 2.

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