SARS-CoV-2 Infection among Serially Tested Emergency Medical Services Workers

A review of infectious disease epidemiology in emergency medical service clinicians

BACKGROUND

The emergency medical service (EMS) workforce is at high risk of occupationally-acquired infections. This review synthesized existing literature on the prevalence, incidence, and severity of infections in the EMS workforce.

METHODS

We searched PubMed, Embase, CINAHL, and SCOPUS from January 1, 2006 to March 15, 2022 for studies in the US that involved EMS clinician or firefighter populations and reported 1 or more health outcomes related to occupationally-acquired infections.

RESULTS

Of the 25 studies that met the inclusion criteria, most focused on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, with prevalence rates ranging from 1.1% to 36.2% (median 6.7%). The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in 4 studies ranged from 1.9% to 6.4%, and the prevalence of Hepatitis C in 1 study was 1.3%. Few studies reported incidence rates. The prevalence or incidence of these infections generally did not differ by age or gender, but 4 studies reported differences by race or ethnicity. In the 4 studies that compared infection rates between EMS clinicians and firefighters, EMS clinicians had a higher chance of hospitalization or death from SAR-CoV-2 (odds ratio 4.23), a higher prevalence of Hepatitis C in another study (odds ratio 1.74), and no significant difference in MRSA colonization in a separate study.

CONCLUSIONS

More research is needed to better characterize the incidence and severity of occupationally-acquired infections in the EMS workforce.

Differences in Motivating Factors for SARS-CoV-2 Vaccination and Perceptions of Infection Risk among Healthcare and EMS Personnel in South Carolina

OBJECTIVES

Although medical workers were prioritized to receive the coronavirus disease 2019 (COVID-19) vaccination, many have declined. Even though studies have investigated differences in COVID-19-related attitudes and vaccination for workers in hospitals and long-term care facilities, none have included emergency medical services (EMS) personnel. We investigated the association between type of medical worker (EMS vs healthcare worker [HCW]) and COVID-19 vaccination, vaccine beliefs, vaccine motivators, personal protection behaviors, and risk perceptions.

METHODS

The data for self-identified HCWs came from surveys distributed to randomly selected residents of South Carolina and EMS personnel recruited at a targeted surveillance testing event during the South Carolina EMS Symposium. Pearson χ2 and Fisher exact tests analyzed differences in the distribution of demographic characteristics and self-reported COVID-19 vaccination attitudes by medical workers. Multivariable logistic regression assessed the association between COVID-19 vaccination and type of medical worker, adjusting for age, sex, race, and frontline status, and assessed the associations among vaccine beliefs, vaccine motivators, personal protection behaviors, and risk perceptions by type of medical worker, adjusting for age, sex, race, frontline status, and vaccination status.

RESULTS

Of the 126 respondents 57.9% were EMS, 42.1% were HCWs, and 73.6% of the cohort were self-reported frontline medical workers. Approximately two-thirds of respondents received a vaccine for COVID-19, with no significant differences between EMS and HCWs; however, EMS workers were significantly less likely to receive the vaccination out of concern about exposures at work/school (adjusted odds ratio [aOR] 0.22, 95% confidence interval [CI] 0.08-0.57), concern about exposures within the community (aOR 0.18, 95% CI 0.07-0.48), or to do their part to control the pandemic (aOR 0.20, 95% CI 0.06-0.69). EMS workers also were significantly less likely to wear a mask all/most of the time when outside the home (aOR 0.04, 95% CI 0.0-0.21) and less concerned about the spread of COVID-19 in their community as compared with HCWs (aOR 0.19, 95% CI 0.06-0.56).

CONCLUSIONS

EMS personnel were significantly less concerned about the spread of COVID-19 in their community and significantly less likely to wear a mask all/most of the time while outside the home as compared with HCWs. Differences in the COVID-19-related attitudes and personal protection behaviors of EMS personnel should be used to develop targeted interventions to increase vaccine motivation and adherence to personal protection protocols.

SARS-CoV-2 seroprevalence among firefighters in Los Angeles, California

Objective

We estimate the seroprevalence of SARS-CoV-2 antibodies among a sample of firefighters in the Los Angeles (LA), California fire department in October 2020 and compare demographic and contextual factors for seropositivity.

Methods

We conducted a serological survey of firefighters in LA, California, USA, in October 2020. Individuals were classified as seropositive for SARS-CoV-2 if they tested positive for IgG, IgM or both. We compared demographic and contextual factors for seropositivity.

Results

All firefighters in LA, California, USA were invited to participate in our study, but only roughly 21% participated. Of 713 participants with valid serological data, 8.8% tested positive for SARS-CoV-2 antibodies, and among the 686 with complete survey data 8.9% tested positive for antibodies. Seropositivity was not associated with gender, age or race/ethnicity. Seropositivity was highest among firefighters who reported working in the vicinity of LA International Airport, which had a known outbreak in July 2020.

Conclusions

Seroprevalence among firefighters in our sample was 8.8%, however, we lack a full workplace seroprevalence estimate to compare the relative magnitude against general population seroprevalence (15%). Workplace safety protocols, such as access to personal protective equipment and testing, can mitigate increased risk of infection at work, and may have eliminated differences in disease burden by geography and race/ethnicity in our sample.

Anti-SARS-CoV-2 IgA Identifies Asymptomatic Infection in First Responders

Background

IgA is an important component of the early immune response to SARS-CoV-2. Prior serosurveys in high-risk groups employing IgG testing alone have provided discordant estimates. The potential added benefit of IgA in serosurveys has not been established.

Methods

Longitudinal serosurvey of first responders (police, emergency medical service providers, fire fighters, and other staff) employing three serologic tests: anti-spike IgA, anti-spike IgG, and anti-nucleocapsid IgG correlated with surveys assessing occupational and non-occupational risk, exposure to COVID-19 and illnesses consistent with COVID-19.

Results

Twelve percent of first responders in Colorado at baseline and 22% at follow-up were assessed as having SARS-CoV-2 infection. Five percent at baseline and 6% at follow-up were seropositive only for IgA. Among those IgA positive only at baseline, the majority 69% had a positive antibody at follow-up. 45% of those infected at baseline and 33% at follow-up were asymptomatic. At all time points, the estimated cumulative incidence in our study was higher than that in the general population.

Conclusions

First responders are at high risk of infection with SARS-CoV-2. IgA testing identified a significant portion of cases missed by IgG testing and its use as part of serologic surveys may improve retrospective identification of asymptomatic infection.

Risk for Acquiring Coronavirus Disease Illness among Emergency Medical Service Personnel Exposed to Aerosol-Generating Procedures

We investigated the risk of coronavirus disease (COVID-19)- patients transmitting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to emergency medical service (EMS) providers, stratified by aerosol-generating procedures (AGP), in King County, Washington, USA, during February 16-July 31, 2020. We conducted a retrospective cohort investigation using a statewide COVID-19 registry and identified 1,115 encounters, 182 with ≥1 AGP. Overall, COVID-19 incidence among EMS personnel was 0.57 infections/10,000 person-days. Incidence per 10,000 person-days did not differ whether or not infection was attributed to a COVID-19 patient encounter (0.28 vs. 0.59; p>0.05). The 1 case attributed to a COVID-19 patient encounter occurred within an at-risk period and involved an AGP. We observed a very low risk for COVID-19 infection attributable to patient encounters among EMS first responders, supporting clinical strategies that maintain established practices for treating patients in emergency conditions.

Frame to Improve the Fit of N95 Filtering Face Mask Respirators

OBJECTIVE

Test a device that can improve upon the seal of filtering face mask respirators (FFRs).

METHODS

A 3-D prototype for a fit improvement frame (FIF) was created and quantitative fit testing was performed for FFRs with and without the FIF.

RESULTS

Thirty eight volunteers underwent fit testing. The overall fit pass rate was 100% for the 3M model 1860 masks, 50% for the 3M model 8511 masks, 13% for the BYD CARE model DE2322, and 7% for the Honeywell DC300N95. When using the FIF the overall passing rate increase to 87% for the DE2322 + FIF (P < 0.01) and for the DC300N95 + FIF the passing rate increase to 73% (P < 0.01).

CONCLUSION

The FIF is effective in improving the mask fit of a common flat fold N95 masks and potentially other N95 masks.

SARS-CoV-2 IgG Seropositivity and Acute Asymptomatic Infection Rate among Firefighter First Responders in an Early Outbreak County in California

Objective: Firefighter first responders and other emergency medical services (EMS) personnel have been among the highest risk healthcare workers for illness during the SARS-CoV-2 pandemic. We sought to determine the rate of seropositivity for SARS-CoV-2 IgG antibodies and of acute asymptomatic infection among firefighter first responders in a single county with early exposure in the pandemic. Methods: We conducted a cross-sectional study of clinically active firefighters cross-trained as paramedics or EMTs in the fire departments of Santa Clara County, California. Firefighters without current symptoms were tested between June and August 2020. Our primary outcomes were rates of SARS-CoV-2 IgG antibody seropositivity and SARS-CoV-2 RT-PCR swab positivity for acute infection. We report cumulative incidence, participant characteristics with frequencies and proportions, and proportion positive and associated relative risk (with 95% confidence intervals). Results: We enrolled 983 out of 1339 eligible participants (response rate: 73.4%). Twenty-five participants (2.54%, 95% CI 1.65-3.73) tested positive for IgG antibodies and 9 (0.92%, 95% CI 0.42-1.73) tested positive for SARS-CoV-2 by RT-PCR. Our cumulative incidence, inclusive of self-reported prior positive PCR tests, was 34 (3.46%, 95% CI 2.41-4.80). Conclusion: In a county with one of the earliest outbreaks in the United States, the seroprevalence among firefighter first responders was lower than that reported by other studies of frontline health care workers, while the cumulative incidence remained higher than that seen in the surrounding community.