Prevalence and predictors of SARS-CoV-2 seropositivity among volunteer firefighters (October 2020 - August 2021)

BACKGROUND AND AIM: First responders are at increased risk of SARS-CoV-2 infection (COVID-19). In the US, 67% of firefighters serve as volunteers, yet few studies have assessed COVID-19 prevalence and predictors within this occupational group. The aim of this cross-sectional study was to assess SARS-CoV-2 seropositivity in US volunteer firefighters enrolled in the Cancer Assessment and Prevention Study (CAPS), a research partner of the Fire Fighter Cancer Cohort Study (FFCCS). METHODS: Between October 2020 and August 2021, 124 non-COVID-19 vaccinated firefighters from ten New Jersey (US) volunteer departments were tested for SARS-CoV-2 seropositivity (IgM and/or IgG). They were compared to seronegative firefighters by firefighting characteristics (# monthly calls; years of firefighting) and demographics (age, sex, education, marital status) using Fisher’s exact and Wilcoxon’s rank tests; associations were explored using multivariable logistic regression. RESULTS: SARS-CoV-2 seroprevalence was 12.1% (n=15). Participants were predominately male (94.4%) and non-Hispanic White (86.3%). Compared to seronegative participants, seropositive participants responded to fewer monthly calls (median (IQR) 9 (7.0, 15.0) vs. 15 (10.0, 25.0)), were younger (median (IQR) 39.3 (24.2, 56.3) vs. 47.0 (34.5, 59.1) years), and a higher proportion were non-White and/or Hispanic (26.7% vs. 9.2%). In multivariable analysis, participants responding to fewer monthly calls had lower odds of SARS-CoV-2 seropositivity (OR 0.91; 95% CI: 0.84, 0.98), adjusting for age and years of firefighting. CONCLUSIONS: There was a high seroprevalence of SARS-CoV-2 among this cohort of volunteer firefighters. The inverse association between median number of monthly firefighting calls was unexpected. Among firefighters who respond to more calls, this finding may be attributable to: better adherence to infection control measures; increased use of personal protective equipment (PPE); and/or exposure to COVID-19 at their primary occupation. The small number of cases means that these results should be interpreted with caution. KEYWORDS: firefighter, SARS-CoV-2, cross-sectional, seroprevalence