Hot Topics in Infection Prevention: COVID and the Great Outdoors, Vaccine Access

Infectious disease transmission isn’t as simple as a singular label that doesn’t describe the nuance or situations that increase or decrease risk.

Outdoor COVID-19 Transmission and Updated Science Brief

This week was a tough one for science communication. A guideline released regarding outdoor masks noted that less than 10% of transmission occurs outside, which was quickly picked up and frankly, likely conflated. Outdoor transmission is exceedingly rare and when it does occur, it involves crowds (close contact for a prolonged period of time) and/or some indoor elements. As New York Times columnist David Leonhardt notes: “That benchmark ‘seems to be a huge exaggeration,’ as Dr. Muge Cevik, a virologist at the University of St. Andrews, said. In truth, the share of transmission that has occurred outdoors seems to be below 1 percent and may be below 0.1 percent.” While the Centers for Disease Control and Prevention (CDC) may have opted for a high benchmark to communicate the higher end of risk, it’s ultimately been a sticking point for many.

A new scientific brief from the CDC last week also clarified a bit more on the nuances of COVID-19 transmission. Within this new brief, the CDC clarifies and details a bit more of transmission in terms of inhalation, deposition of the virus on exposed mucous membranes, and touching mucous membranes with contaminated hands. The brief discusses inhalation of respiratory droplets and aerosol particles, which can remain suspended in the air longer.

Overall, the brief is quite helpful in communicating this nuance, and reiterates two points of importance—our current infection prevention efforts are still effective and risk of transmission is greatest within 3-6 feet of an infectious individual.

There have been heated discussions around the terminology and communication of transmission, with many demanding that it be classified as “airborne,” but ultimately this guidance reiterates risk and nuance in the face of novel pathogens. Overall, it’s helpful in understanding the efficacy of interventions, reriating how we can communicate that close contact is the primary risk for transmission, but that transmission can and does occur beyond six feet.

As the CDC notes regarding these clusters—“These transmission events have involved the presence of an infectious person exhaling virus indoors for an extended time (more than 15 minutes and in some cases hours) leading to virus concentrations in the air space sufficient to transmit infections to people more than 6 feet away, and in some cases to people who have passed through that space soon after the infectious person left. Per published reports, factors that increase the risk of SARS-CoV-2 infection under these circumstances include:

  • Enclosed spaces with inadequate ventilation or air handling within which the concentration of exhaled respiratory fluids, especially very fine droplets and aerosol particles, can build up in the air space.
  • Increased exhalation of respiratory fluids if the infectious person is engaged in physical exertion or raises their voice (e.g., exercising, shouting, singing).
  • Prolonged exposure to these conditions, typically more than 15 minutes.

Such updates are appreciated for not only health care response, but also as we communicate with health care workers and communities. Infectious disease transmission isn’t as simple as a singular label that doesn’t describe the nuance or situations that increase or decrease risk, so moving forward these communication strategies and resources are appreciated.

Entire Countries Need Better Access to COVID-19 Vaccines

This week the Food and Drug Administration (FDA) expanded the emergency use authorization (EUA) of the Pfizer COVID-19 vaccine to include those aged 12-15. Previously, the vaccine was recommended for those 16 and older. As more attention turns to schools and what the fall will look like, this comes as a welcome relief to many. “Today's action allows for a younger population to be protected from COVID-19, bringing us closer to returning to a sense of normalcy and to ending the pandemic,” said Acting FDA Commissioner Janet Woodcock, MD, in a press release. “Parents and guardians can rest assured that the agency undertook a rigorous and thorough review of all available data, as we have with all of our COVID-19 vaccine emergency use authorizations." Over 1.5 million children between 11-17 years have been infected with COVID-19 since last March and right now, the biggest concern for this rollout is on hesitancy. The CDC and FDA are working with schools and pediatricians to address this and ensure widespread vaccine availability. This is a positive step forward for COVID-19 mitigation in the United States, but as many have noted, as we are expanding our vaccination distribution, most countries around the world are struggling. COVID-19 is a global issue and vaccine distribution is wholly unequitable.