COVID-19: The ever-changing pandemicAug 2, 2021
Over the last several weeks, the message of a return to using masks has been controversial—a controversy initially sparked by a mask mandate for Los Angeles County issued on July 19. At the time, the CDC and President Biden stood firm that masks were not needed for controlling transmission of SARS-CoV-2. However, revised guidelines were released by the CDC on July 27. Among the changes is “…a recommendation for fully vaccinated people to wear a mask in public indoor settings in areas of substantial or high transmission,” and “CDC recommends universal indoor masking for all teachers, staff, students, and visitors to schools, regardless of vaccination status.”
The CDC based the guideline changes on new evidence related to the transmissibility of the Delta variant, particularly among the vaccinated. Its decision-making appears to have been swayed by key findings from outbreaks in Barnstable County, Massachusetts, which occurred after large gatherings among mostly vaccinated participants. Although the place was not described in the CDC's Morbidity, Mortality, and Weekly Reports, the gatherings took place in Provincetown as thousands partied over the July 4 weekend. Of the 469 cases identified, 74% were in fully vaccinated persons. The viral loads were comparable in vaccinated and unvaccinated COVID-19 persons, implying that vaccination may not reduce Delta variant transmission, even though it reduces the severity of COVID-19.
Further rationale for the changes is apparently contained in a “leaked” CDC report, a presentation labeled “Improving communications around vaccine breakthrough and vaccine effectiveness.” That document reviews the rising frequency of breakthrough cases, information on vaccine effectiveness against the Delta variant, the high viral load with the Delta variant, and vaccine efficacy in high-risk populations. It also includes undocumented modeling results that indicate a benefit of masking, assuming some effectiveness for both source control and personal protection. One conclusion in the materials is linked to the modeling: “Given higher transmissibility and current vaccine coverage, universal masking is essential to reduce transmission of the Delta variant.” In a speech on Thursday, President Biden pleaded for Americans to be vaccinated and commented: “We need to wear masks to protect each other and to stop the rapid spread of this virus as we work to get more people vaccinated.”
The message is the right one and I continue to view masking as a “no regrets” strategy from the public health perspective that has been unnecessarily politicized and tarnished. The CDC claims to be “following the science” as it should, but a lack of transparency as to the “science” that is driving decision-making is troubling. The findings of the Massachusetts outbreaks are compelling and invite changes in how the epidemic is modeled. However, a “leaked report” and undocumented model findings leading to a far-reaching conclusion are insufficiently transparent to publicly justify a major change in the CDC’s guidelines.
Last week’s ColoradoSPH Town Hall on Dismantling Structural Racism and Advancing Inclusive Excellence was attended by 120 people and covered the many activities across the school that have launched over the year since the July 2020 Town Hall. A summary and other materials will be posted.
Jonathan Samet, MD, MS
Dean, Colorado School of Public Health