CDC Updates Guidance to Include Double-Masking

Two masks might be better than one. That’s the gist of guidance handed down today by the Centers for Disease Control and Prevention (CDC) in the face of growing concern about more contagious and deadlier variants of coronavirus disease 2019 (COVID-19) circulating through the population of the United States. The updated guidance is based on findings published today in a study in the CDC’s Morbidity and Mortality Weekly Report.

It all depends on the fit, according to CDC investigators.

“CDC conducted experiments to assess two ways of improving the fit of medical procedure masks: fitting a cloth mask over a medical procedure mask, and knotting the ear loops of a medical procedure mask and then tucking in and flattening the extra material close to the face,” the MMWR study states. “Each modification substantially improved source control and reduced wearer exposure.”

Health care professionals, including infection preventionists, question whether double-masking might make their job more difficult. That was the main point iterated by Infection Control Today® Editorial Advisory Board MemberSaskia v. Popescu, PhD, MPH, MA, CIC, in a website post on Monday. The subject first surfaced when Anthony Fauci, MD, the director of the National Institute of Allergy and Infectious Diseases, wore two masks recently.

“There are some things to remember—not a lot of studies have been done on cloth mask quality, let alone double-masking,” Popescu wrote. “The strategy is theoretical but rooted in the notion of a mask that fits well and has layers of filtration will ultimately protect the wearer and those around them. A single mask that fits you and has multiple layers is better than two that don’t fit you well.”

About today’s updated guidance, Popescu says that “it’s helpful to have published data on improving cloth or community masks as that’s been an overall gap in the research. This study helps address the fit piece that we often struggle with in the community where cloth masks and procedural masks are more widely available and used.”

The CDC issued the guidance with eye on the COVID-19 variants that have recently surfaced. The B.1.1.7 variance, for instance, is anywhere from 50% to 70% more contagious and 30% deadlier. It has spread to 86 countries and US health officials worry that it may soon become the dominant variant.

“We know that universal masking works,” John T. Brooks, MD, the CDC’s medical officer tells the Washington Post. “And now these variants are circulating … whatever we can do to improve the fit of a mask to make it work better, the faster we can end this pandemic.”

The MMWR study concludes: “Controlling SARS-CoV-2 transmission is critical not only to reduce the widespread effects of the COVID-19 pandemic on human health and the economy but also to slow viral evolution and the emergence of variants that could alter transmission dynamics or affect the usefulness of diagnostics, therapeutics, and vaccines. Until vaccine-induced population immunity is achieved, universal masking is a highly effective means to slow the spread of SARS-CoV-2 when combined with other protective measures, such as physical distancing, avoiding crowds and poorly ventilated indoor spaces, and good hand hygiene. The data in this report underscore the finding that good fit can increase overall mask efficiency. Multiple simple ways to improve fit have been demonstrated to be effective. Continued innovative efforts to improve the fit of cloth and medical procedure masks to enhance their performance merit attention.”

Popescu agrees with the “combined with other protective measures” phrase, believing in the Swiss cheese method of infection prevention and control. In her Monday posting, she wrote: “A single mask that fits you and has multiple layers is better than two that don’t fit you well. When making the decision to single- or double-mask, the conversation and strategy should focus on the two key pieces—fit and filtration. Masks are a critical piece to COVID-19 prevention, but not the only one and while we discuss double- or single-masking, it’s important not to lose track of all the pieces to COVID prevention. Risk reduction is additive and a well-fitted and filtered mask is one piece to this prevention strategy.”

The CDC’s backing of double-masking comes on the heels of another MMWR study that says that states that mandated that residents must wear masks faired much better than those that didn’t. That study states that hospitalizations for COVID-19 dropped by a statistically significant 5.5 percentage points for adults from 18 to 64, compared to the hospitalization rates in the 4 weeks preceding the implementation of the mask mandates. For people 40- to 64-years old, mask mandates resulted in a 2.9 percentage point reduction in hospitalizations for COVID-19 3 weeks or less after the mask mandate, but this age group also saw a 5.5 percentage-point decline in hospitalizations at 3 weeks or more. Hospitalization rates for adults over 65 also declined 3 weeks after the mask mandate, though those declines were not statistically significant, the study states. But the lesser decline in the oldest age group may have been because people that age were more inclined to wear a mask in the first place.

Will wearing a mask become a national mandate? President Biden has signed executive orders that say masks must be worn on buses, trains, planes and on federal property. Meanwhile, 36 state governments have mandated that masks be worn in public, according to the AARP.