Two Masks Better Than One: US CDC Advises Double Or ‘Tight-Fit’ Masks To Stave Off More Infectious COVID Variants

The United States Centers for Disease Control has issued new guidance for “tight fit” or “double masks” that it says can filter out over 90% of SARS-CoV2 viruses – much higher averages than if either mask were worn loosely or on its own.

The guidance, issued as the US along with other countries face an onslaught of more infectious virus variants, including a variant B117, first identified in the United Kingdom, rapidly expanding across the world, and believed to be 40-70% more infectious than the variants that were prevalent in 2020.

The CDC recommendation was based upon a series of studies that examined virus penetration through various types of masks, which are widely available to the general public.

The recommendations are based on a new series of experiments that the CDC conducted to assess ways of improving the fit and protective capacity of simple surgical masks (also called medical procedure) masks on their own, or in combination with cloth masks.  According to the new recommendation, the two modifications that “substantially improved’ exposure were:

  • Fitting a cloth mask over a medical procedure mask;
  • Knotting the ear loops of a medical procedure mask and then tucking in and flattening the extra material close to the face.

The two innovations help improve the fit of the mask around the face – preventing air leakage that also allows virus particles in and out, CDC said.

The “double masking” approach involves the use of a three-ply medical procedure mask (surgical masks) covered by a three-ply cloth cotton mask.

While the unknotted medical procedure mask alone blocked 42.0% of the particles from a simulated cough and use of the cloth mask alone blocked 44.3%, the combination of the cloth mask covering the medical procedure mask (double mask) blocked 92.5% of the cough particles, the CDC said in its brief.

Knotting the surgical mask, on the other hand, to give it a “tighter fit” would block about 63% of potentially pathogenic particles emitted someone wearing such a mask, and about 65% of particles to which someone else wearing the tighter-fitting mask might otherwise be exposed.

Nose Wires and Mask Fitters – Other Improvements
Mask fitter or brace
Mask with nose wire

Improvements could also involve using a mask that has a “nose wire”, said the CDC guidance on masking “Dos” and “Don’ts” that was issued just after the release of the study,  Nose wires are a feature of N95 or KN95 masks.  A mask “fitter or brace”  that keeps air from leaking in and out around the face, is another effective modification.

CDC Director Issues Recommednation At White House Briefing

CDC’s director, Rochelle P. Walensky, announced the findings at a White House coronavirus task force briefing Wednesday. She appealed to Americans to wear “a well-fitting mask” that has two or more layers – a measure that is especially critical in light of the fast-expanding array of virus variants in the United States and elsewhere.

Despite the boost provided by vaccine campaigns, Walensky warned the public against relaxing their guard on other “non-pharmaceutical” measures that prevent disease spread.

“With cases hospitalizations and deaths still very high, now is not the time to roll back mask requirements,” she said, adding, “The bottom line is this: masks work and they work when they have a good fit and are worn correctly.”

The “double mask” approach, however, was sported by Chief Medical Advisor Anthony Fauci at the January inauguration of new US President Joe Biden.

Upon his inauguration, President Joe Biden also challenged Americans to wear masks for the first 100 days of his presidency.

The study has limitations: The researchers only tested one brand of surgical mask and one kind of cloth mask in simulations using dummies. But it follows logically that tighter masks, or masks with added layers, would also provide added protection.

However, it is clear that US public health officials feel a sense of urgency with the more contagious B117 variant, first found in Britain, doubling roughly every 10 days in the United States. According to the CDC, it may become the dominant variant in the nation by March.

In Europe, several countries have also issued recommendations to the public to wear N95 masks (also known in Europe as FFP), in order to ensure better protection. WHO, however, has so far resisted such global advice in light of the global shortages of PPE for health workers.  It remains to be seen if in the wake of the CDC recommendations, however, the global health agency might issue updated advice on tighter-fitting or double masking measures.   For the moment, WHO was sticking to general messages:

“Please remember – fit, filtration and breathability are all critical for optimal performance.  Wear them well, wear them appropriately, wear them safely,” said WHO’s Maria Van Kerhkove in a Tweet Wednesday responding to the CDC recommendations.



Image Credits: US Centers for Disease Control , US CDC .

Combat the infodemic in health information and support health policy reporting from the global South. Our growing network of journalists in Africa, Asia, Geneva and New York connect the dots between regional realities and the big global debates, with evidence-based, open access news and analysis. To make a personal or organisational contribution click here on PayPal.