Background: Among all U.S. jobs, those employed as first responders (e.g. firefighters) are at an increased risk for COVID-19 infection. Strategies that limit the spread of the SARS-CoV-2 virus within their workforce, to those they provide care, and inform on return to work algorithms are needed. In the present study, we estimate the point seroprevalence of SARS-CoV-2 antibodies in the frontline workforce of a Florida fire department located in the epicenter of the outbreak.

Methods: A cross-sectional study design was used to estimate the point seroprevalence of SARS-CoV-2 antibodies using a rapid IgM-IgG combined point-of-care lateral flow immunoassay collected over a two-day period. Fire department personnel were emailed a survey link assessing COVID-19 symptoms and work exposures the day prior to their scheduled antibody test. Off-and on-duty firefighters drove through the fire station/training facility in their personal vehicles or on-duty engine/rescue trucks for SARS-CoV-2 antibody testing.

Results: Among the 203 firefighter participants, 8.9% of the workforce resulted positive for SARS-CoV-2 antibodies (IgG only, IgM only, or IgG/IgM). The average number of COVID-19 case contacts was significantly higher (13.3±4.8 contacts vs. 7.31±4.8; p=.022) among antibody positive firefighters compared to firefighters without antibodies. The proportion of firefighters who reported symptoms in the 2 weeks prior to antibody testing was higher for those who tested antibody positive compared to firefighters who were antibody negative (22.2% vs. 7.7%; p=0.041).

Conclusion: Rapid SARS-CoV-2 IgM-IgG antibody testing documented early and late stage infection in a firefighter workforce providing insight on return to work algorithms for firefighters.