Occupation and Incident Breakthrough Infections With SARS-Cov-2 in a Cohort of Frontline Workers During Delta and Omicron Predominance

Abstract

Background: The SARS-CoV-2 virus has caused a pandemic with an unprecedented number of infections and deaths. Research conducted prior to vaccine availability has identified first responders at increased risk of experiencing infections, but occupational risk profiles accounting for vaccination status may have shifted. We examined data from the longitudinal cohort study The Arizona Healthcare Emergency Response and Other Essential workers Surveillance study (AZ HEROES) to determine if healthcare personnel, first responders, or other essential workers were at increased risk of experiencing a breakthrough COVID-19 infection between the periods of Delta and Omicron predominance. Methods: Breakthrough infections within the AZ HEROES study were confirmed through laboratory specimens among participants. Within the Delta (06/14/2021-12/13/2021) and Omicron (12/14/2021-02/16/2022) periods, 697 were at risk for breakthrough infection during Delta and 1,260 were at risk during Omicron. Breakthrough infections were defined as infections occurring at least 14 days from the primary series of the vaccine, and assessed for each period, examining crude incidence among granular occupational categories and the association between breakthrough infection and occupation using cox proportional hazards models among healthcare personnel, first responders, and other essential workers. The models were adjusted for baseline demographics, underlying health status, days since vaccination, and mitigation behaviors. Results: Fewer breakthrough infections were reported in the Delta period (n=46) compared to the Omicron period (n=241), despite fewer person-days at risk observed during Omicron (Median (IQR): 64 (0) vs 183 (0)) compared to Delta. Compared to healthcare personnel and other essential workers, first responders were more likely to experience a breakthrough infection. In the Delta period, first responders were 186% more likely to experience breakthrough infections (compared to the healthcare personnel: (HR: 2.86 (95% CI 1.21, 6.77) p=0.02) compared to other essential workers: (HR: 1.99 (95% CI: 0.92, 4.29) p=0.08)). In the Omicron period, first responders were 54% more likely to experience breakthrough infections (compared to healthcare personnel: (HR: 1.54 (95% CI 1.07, 2.21) p=0.02) compared to other essential workers: (HR: 1.92 (95% CI: 1.34, 2.75) p=0.0003)). Testing for interaction between occupation and predominant variant confirmed that the association between risk and breakthrough infection and occupation did not differ by variant (p=0.41). Conclusion: The finding that first responders are at increased risk for breakthrough infection align with previous findings of elevated risk during the pre-vaccine era. This approach provides a unique perspective to better understand the role that occupation has as an exposure factor for COVID-19 infection. Future research should strive to examine the factors that put first responders at increased risk to develop targeted interventions.