Emergency Medical Responders Largely Protected From COVID: Study

SEATTLE — Though emergency medical service first responders are often called to help patients infected with COVID-19, EMS staff's on-the-job infection rate remains low.

According to a new study by UW Medicine, that's because personal protective equipment (PPE) is working to safeguard workers from high volumes of respiratory aerosols.

“Our findings should help reassure first responders that emergency care in general, and specifically when performing aerosol-generating procedures, can be delivered safely to patients as long as personal protective gear is properly deployed,” said lead researcher Dr. Thomas Rea.

The study, a collaborative effort between the University of Washington School of Medicine and Public Health – Seattle & King County Division of Emergency Medical Services, was published this week in the journal Emerging Infectious Diseases. For their work, researchers looked at 3,000 King County EMS workers from mid-February through July 2020, tracking which of the workers were "potentially exposed to COVID-19" and which ended up contracting the disease.

Researchers say they considered an EMS provider potentially exposed if they treated a patient who had tested positive for COVID-19 within ten days before or three days after their encounter.

Using that metric, researchers found that 1,592 of the 3,000 EMS providers cared for 946 different COVID-19 patients, for a total 3,710 encounters between EMS staff and COVID-19 positive patients. Of the 1,592 EMS staff who interacted with COVID-19 patients:

• 655, or 41 percent, had one encounter with a positive patient.
• 417, or 26 percent, had two encounters.
• 520, or 33 percent, had three or more encounters.
• In 182 encounters, the EMS staff had to perform an intubation or other procedure which would have generated a large volume of respiratory aerosols.

However, despite all of those potentially-infectious incidents, just one of the 1,592 exposed providers tested positive for COVID-19 afterwards. Extrapolating from that, researchers found EMS workers faced an "extremely low" incidence rate of 0.28 cases per every 10,000 person-days.

Researchers credit that low rate to the consistent use of PPE, like masks, eye protection, gloves and a gown. They also say the study may have applications outside the ambulance, because it highlights the importance and usefulness of social distancing, mask use, and frequent handwashing.

"Sources of infectious risk for EMS personnel are not confined to patients. We observed that the large majority of COVID-19 illness was a consequence of encounters not with patients but in the community or occupational settings," the study reads. "These findings support efforts to screen workplaces for provider symptoms or initiate point-of-care provider testing to limit on-the-job exposure as well as to practice guideline-directed social distancing, masking, and hygiene recommendations outlined for the general public, acknowledging that vaccination may affect these directives."

As a caveat, researchers do note that their study took place before the rapidly-spreading delta strain became the dominant form of coronavirus in Washington, and that their findings may have been different had it been around or had vaccines been available.

"While provider vaccination might further reduce patient-provider transmission risk, the delta variant could increase risk, as it is more contagious," Rea said. "The balance of these two new factors is uncertain in this setting and provides impetus to continue to evaluate occupational risk."