Dean's Notes

Quite a week: many Colorado counties moved to “Level Clear,” and the Centers for Disease Control and Prevention relaxed its mask guidelines for those who are vaccinated. Turning to Level Clear, adopted by six Denver metro area counties and in force on May 16, most transmission control restrictions are removed. For those who are vaccinated, the CDC guidelines changed last week as well: “Fully vaccinated people can resume activities without wearing a mask or physically distancing, except where required by federal, state, local, tribal, or territorial laws, rules, and regulations, including local business and workplace guidance.” Governor Polis changed the guidelines for Coloradans to mirror the CDC changes. 

The New York Times, among other media, has commented on the seeming confusion with the change in guidelines. Some states and local governments have changed mask requirements to follow CDC while others have not, and businesses and employers are now setting their own policies. The result is a patchwork, perhaps best solved by carrying a mask and wearing it when you think that you should. For now, self-reporting will remain the basis for ascertaining vaccination status. At least, transmission outdoors has been declared as posing little risk and masks are no longer needed outdoors. I have stopped using one while cycling and hiking, although a neck gaiter is useful when evening insects are out. 

Why is there confusion on this fundamental public health measure? There is no central agency concerned with respiratory health protection. By statute, the Occupational Safety and Health Administration (OSHA) has respiratory protection programs for selected worker groups as does the Mine Safety and Health Administration. For workers not covered in these or other specific programs and for the public, however, no entity is charged with developing, implementing, and assuring a respiratory protection program. The American Society of Testing and Materials (ASTM) has a new standard for barrier face coverings, representing a starting point. We lack a broader framework for providing personal protective equipment (PPE) when needed, whether during a pandemic or during an air pollution episode from wildfire smoke. I chair a committee of the National Academies of Sciences, Engineering, and Medicine: Committee on Respiratory Protection for the Public and Workers without Respiratory Protection Programs at their Workplaces. We are charged with outlining a framework to address this and other gaps, but the committee’s work will not be complete, nor will our report be published until 2022.

Relevant to respiratory protection, CDC changed its guidance on airborne transmission of SARS-CoV-2 on May 7 with a clear acknowledgement of the importance of smaller particles (aerosols). The World Health Organization has updated its guidance as well to better reflect the role of aerosols in transmission of the virus. An April 15 comment in The Lancet, succinctly lays out the main points of scientific evidence supporting airborne transmission by aerosols. An essay in The New York Times by Zeynep Tufecki ponders the delay in acknowledging the role of aerosol transmission and its consequences. Beyond PPE, airborne transmission by aerosols provides a rationale for a close look at building design and ventilation, a topic addressed in a recent commentary in Science. Hopefully, the COVID-19 pandemic will prompt a rethinking of building design and operation to better control indoor transmission of infection. 

Turning back to Level Clear, somewhat of a misnomer since the pandemic continues in Colorado, the designation and the associated actions reflect anticipation that the epidemic curve will maintain a downward trajectory for the months to come. After several months of an increasing epidemic curve, a sustained downward trajectory seems certain as vaccination rates continue to rise. Yesterday, the number of people hospitalized with COVID-19 continued its weeklong descent (from 679 to 563). However, the descent starts at a relative high point with approximately one percent of Coloradans infected at present. 

My skills in weather prognostication remain dubious. Snow is gone but replaced by unrelenting clouds and predictions of rain. 

Jonathan Samet, MD, MS
Dean, Colorado School of Public Health