Workplace
Table 1 continued
COVID-19 antibody test result
Total sample N N (%)*
Positive (IgG, IgM or IgG/IgM) n (%)*
Negative n (%)*
Characteristics
P value
Average COVID-19 case contacts
0.022
Average cases±SD
7.73 ± 6.3
13.3 ± 4.8
7.31 ± 6.2
Average time spent with COVID-19 positive person
0.025
Less than 5 min
15 (17.0) 66 (75.0)
6 (42.9) 8 (57.1) 0 (0.0)
9 (12.2) 58 (78.4)
5–30 min
Greater than 30 min
7 (8.0)
7 (9.5)
Used any PPE during COVID-19 encounter
0.383
Yes, any PPE No PPE use
87 (93.5)
6 (85.7) 1 (14.3)
81 (94.2)
6 (6.5)
5 (5.8)
Number of PPE items used with COVID-19 positive person
0.79
Average count PPE used (one to six items) 3.3 ± 1.4 *Differences in subtotal population sample due to item non-response or missing. Case contact=when a firefighter was within 6 feet of an infected person (laboratory-confirmed or probable COVID-19 patients) for at least 15 min; COVID-19 positive person indicates an individual with laboratory-confirmed COVID-19 test; PPE items included gloves, double gloves, N-95 respirator, fluid resistant sleeves, eye protection and gown. EMT, Emergency Medical Technician; GED, General Educational Development; Ig, immunoglobulin; PPE, personal protective equipment. 3.3 ± 1.4 3.1 ± 1.6
drove through the antibody testing fire station in their personal vehicles or on-duty engine/rescue trucks for SARS-CoV-2 anti- body testing. Off-duty firefighters/paramedics could wait in the fire station parking lot for 10–15 min to receive the results of their antibody test, while on-duty personnel were instructed to return to their fire station immediately. The fire department infec- tion control officer (ICO) followed up directly with any on-duty firefighter personnel who tested positive for SARS-CoV-2 anti- bodies. The ICO immediately quarantined the firefighter/para- medic, conducted reflex nasal swab (reverse transcription PCR (RT-PCR)) testing and closely monitored coworker firefighters at the fire station as part of the comprehensive F-TRACE project. A total of three firefighters/paramedics did not participate in the surveillance project, of which two were out of the geographic area because of scheduled vacation and one declined to partici- pate for religious reasons (response rate=98.6%). Study survey measures and administration Firefighters/paramedics were asked to complete two web-based survey instruments (ie, an intake form and a COVID-19 expo- sure form) prior to their scheduled antibody testing day. Survey instruments were administered to firefighters/paramedics via an email link sent by fire department leadership using REDCap, a secure web-based application for building and managing complex online surveys and databases. 10 The intake form consisted of a 30-item questionnaire assessing sociodemographic (ie, age, sex, race, ethnicity, educational attainment, marital status, height/ weight and contact information) and work characteristics (ie, station assignment, shift schedule, firefighter tenure, rank, current job tasks, number of fire/EMS calls, second job and mili- tary experience) adapted from questions on federal surveys. 11 The COVID-19 exposure form is comprised of 29 items assessing COVID-19 firefighter/paramedic symptoms, prior COVID-19 testing, COVID-19 contacts, smoking status, receipt of influenza shot in prior 12 months, as well as a series of ques- tions on exposure risk assessing the frequency and duration of COVID-19 patient exposures, PPE use and firefighter coworker contacts adapted from the CDC COVID-19 questionnaire. 12 We assessed the type of PPE used by the firefighter by asking, “Were you using any protective equipment when you came into contact with possible COVID-19 person? Choose all that apply.” Response options included: “gloves, double gloves, N-95 respi- rator, fluid resistant sleeves, eye protection, and gown”. A case
regarding the prevalence of coronavirus in the workforce. Strat- egies that limit the spread of the SARS-CoV-2 virus within their workforce and tools that provide near real-time decision-making on firefighter/paramedics return to work algorithms and infec- tion control strategies are needed. Serological antibody tests, despite their limitations, are critical tools for assessments of SARS-CoV-2 exposure, infection and potential immunity. 4 5 Current testing for the SARS-CoV-2 virus largely depends on labour-intensive molecular techniques that can often be delayed by days, limiting their utility in return to work algorithms for a fast-paced emergency responder workforce. 6 7 Recent studies have documented that asymptomatic individuals might contribute to SARS-CoV-2 transmission, further compli- cating efforts to limit the spread of the virus. 8 9 As part of a complementary and broader comprehensive COVID-19 medical surveillance programme, reliable antibody detection assays would enable more accurate estimates of SARS-CoV-2 prev- alence and incidence in the first responder workforce. A joint collaborative partnership between city government, fire depart- ment, local union and an academic medical centre supported the implementation of the Firefighter Tracking, Resources, and Assessment of COVID-19 Epidemiology (F-TRACE) project, supporting the coordination, tracking and educational resources of COVID-19 contact, presumptive and confirmed cases among fire department personnel. In the present study, we estimate the point seroprevalence of SARS-CoV-2 antibodies among frontline firefighter/paramedics of a South Florida fire department located in the epicentre of a State outbreak. Secondary data analysis of cross-sectional information collected as part of the fire department’s F-TRACE project was used to esti- mate the point seroprevalence of SARS-CoV-2 antibodies among frontline firefighters/paramedics collected over a 2-day period, 16–17 April 2020. Firefighters/paramedics of a US fire depart- ment in Florida were invited by department and local union leadership to voluntarily consent to participate in a one-time surveillance assessment for SARS-CoV-2 antibodies. Fire depart- ment personnel were emailed a survey link assessing COVID-19 symptoms and work exposure characteristics the day prior to the scheduled drive-through antibody testing at a designated fire station. Off-duty and on-duty firefighter/paramedic personnel METHODS Study design, participants and recruitment
Caban-Martinez AJ, et al . Occup Environ Med 2020; 77 :857–861. doi:10.1136/oemed-2020-106676
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