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A Review of Masks Against COVID-19 for Better Protection

  • Authors: WebMD Health News Author: Carolyn Crist; CME Author: Charles P. Vega, MD
  • CME / ABIM MOC / CE Released: 3/31/2021
  • Valid for credit through: 3/31/2022, 11:59 PM EST
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Target Audience and Goal Statement

This activity is intended for primary care clinicians, infectious disease specialists, nurses, pharmacists and other clinicians who care for patients at risk for COVID-19.

The goal of this activity is to evaluate the efficacy of different forms of masks against infection with COVID-19.

Upon completion of this activity, participants will:

  • Compare different types of masks for filtering efficiency for particles similar in size to SARS-CoV-2
  • Analyze the efficacy of modifications for a standard medical procedure mask for filtering particles similar in size to SARS-CoV-2
  • Outline implications for the healthcare team


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Medscape, LLC, encourages Authors to identify investigational products or off-label uses of products regulated by the US Food and Drug Administration, at first mention and where appropriate in the content.

WebMD Health News Author

  • Carolyn Crist


    Disclosure: Carolyn Crist has disclosed no relevant financial relationships.

CME Author

  • Charles P. Vega, MD

    Health Sciences Clinical Professor of Family Medicine
    University of California, Irvine School of Medicine
    Irvine, California


    Disclosure: Charles P. Vega, MD, has disclosed the following relevant financial relationships:
    Served as an advisor or consultant for: GlaxoSmithKline

Editor/CE Reviewer

  • Esther Nyarko, PharmD

    Associate Director, Accreditation and Compliance
    Medscape, LLC


    Disclosure: Esther Nyarko, PharmD, has disclosed no relevant financial relationships.

CME Reviewer/Nurse Planner

  • Stephanie Corder, ND, RN, CHCP

    Associate Director, Accreditation and Compliance
    Medscape, LLC


    Disclosure: Stephanie Corder, ND, RN, CHCP, has disclosed no relevant financial relationships.

Medscape, LLC staff have disclosed that they have no relevant financial relationships.

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A Review of Masks Against COVID-19 for Better Protection

Authors: WebMD Health News Author: Carolyn Crist; CME Author: Charles P. Vega, MDFaculty and Disclosures

CME / ABIM MOC / CE Released: 3/31/2021

Valid for credit through: 3/31/2022, 11:59 PM EST


Note: The information on the coronavirus outbreak is continually evolving. The content within this activity serves as a historical reference to the information that was available at the time of this publication. We continue to add to the collection of activities on this subject as new information becomes available. It is the policy of Medscape Education to avoid the mention of brand names or specific manufacturers in accredited educational activities. However, manufacturer names related to COVID-19 vaccines may be provided in this activity to promote clarity. The use of manufacturer names should not be viewed as an endorsement by Medscape of any specific product or manufacturer.

Clinical Context

Masks are a proven means to prevent the spread of SARS-Cov-2, the virus that causes COVID-19, but a previous study by Sickbert-Bennett and colleagues suggested that not all masks may be equal in this regard. In this study, researchers evaluated 29 nonfitted masks for fitted filtration efficiencies (FFE) in a controlled laboratory environment. Their results were published in the August 11, 2020 issue of JAMA Internal Medicine.[1]

As expected, N95 respirators outperformed other masks, with FFE in excess of 95%; however, a less expected finding was that N95 respirators that had expired or that had been sterilized with ethylene oxide and hydrogen peroxide were still highly effective. KN95 respirators, many of which are produced in China, were substantially less effective, with FFE of 53.2% to 85.1%. Surgical masks with ties offered reasonable efficacy (FFE = 71.5%), but surgical masks with ear loops were associated with an FFE of 38.1% alone.

The current study by Clapp and colleagues provides more evidence regarding the efficacy of masks in preventing the spread of molecules with size similar to SARS-CoV-2. In particular, this study addresses means that purportedly can increase mask effectiveness.

Study Synopsis and Perspective

Centers for Disease Control and Prevention (CDC) officials emphasized the importance of wearing face masks that properly fit the face to slow the spread of SARS-CoV-2, the virus that causes COVID-19.

Mask fitters, which are small reusable devices that cinch a cloth or medical mask, can create a tighter fit against the face.

“Fitters have been scientifically demonstrated to improve filtration performance by as much as 90% or more,” John Brooks, MD, chief medical officer of the CDC’s COVID-19 Response, said January 29 during a media briefing with the Infectious Diseases Society of America.[2]

That range of filtration efficiency meets the same standards as N95 respirators, he said.

“The more choices we can offer people, the more likely they are to find something that suits them and that they’ll adopt,” he said.

Wearing masks remains a key part of slowing the spread of COVID-19, particularly with the new spread of coronavirus variants, Brooks said. He reiterated that masks aren’t a substitute for social distancing and that people should still wear masks when they stand 6 feet apart from others, especially indoors and around those who do not live in the same household.

Throughout the pandemic, the CDC has studied the best combination of materials that block and filter respiratory particles, along with fit, comfort, durability, and consumer appeal.

Double masking, for instance, could be effective to further reduce the spread of the virus, Brooks said. People can wear a cloth mask with a high thread count over a medical mask, where the medical mask acts as a filter and the cloth mask adds an extra layer of filtration that better fits the contour of the face to prevent leaking.

CDC scientists are now conducting experiments to evaluate the efficacy of wearing 2 masks and will share the data as soon as it is available, Brooks said.

“It’s thought that this specific combination of a cloth and a medical mask could block over 90% or more of those respiratory droplets and particles,” he added.

Mask fitters could achieve a similar goal of preventing leakage, he said. For consumers who are interested, mask fitters are available for sale online, and several websites provide instructions on how to make one at home. A smartphone app also allows consumers to scan their face and use a 3D printer to create a better custom fit for the contours of their face.

“Any mask is better than no mask,” he said. “Regardless of what we use, it’s critical that as many of us as possible mask up.”

Study Highlights

  • Clapp and colleagues evaluated the FFE of various consumer-grade and improvised face masks, as well as several popular modifications of medical procedure masks intended to improve mask fit or comfort. Their study results were published online December 10, 2020, in JAMA Internal Medicine.[3]
  • The researchers used a generator that produced particles with a median diameter of 0.05 µm. They tested FFE for different masks while varying the humidity and temperature within a chamber. The test volunteer completed a series of bodily movements in the chamber to validate FFE in different positions.
  • All masks were tested on a single man, who weighed 165 lb and measured 5' 10" tall. The male volunteer had no beard.
  • The investigators tested 7 different masks, as well as 5 modifications to a standard medical procedure mask.
  • The N95 respirator achieved an FFE of 98.4%. The FFE of the other commercially available masks tested ranged from 79% to 26.5%:
    • 3-layer cotton mask with ear loops = 26.5%
    • Polypropylene mask with fixed ear loops = 28.6%
    • Single-layer polyester gaiter/neck cover (balaclava bandana) = 37.8%
    • Single-layer polyester/nylon mask with ties = 39.3%
    • 2-layer nylon mask with ear loops (without aluminum nose bridge) = 44.7%
    • Cotton bandana worn “bandit style” = 49%
    • Cotton bandana folded in a rectangle per Surgeon General’s recommendation = 49.9%
    • 2-layer nylon mask with ear loops (with aluminum nose bridge) = 56.3%
    • Surgical mask with ties = 71.5%
    • 2-layer nylon mask with ear loops (with aluminum nose bridge and 1 insert) = 74.4%
    • 2-layer nylon mask with ear loops (with aluminum nose bridge and no insert; washed once) = 79%
  • In addition, the FFE for the standard medical procedure mask with ear loops were as follows:
    • No alteration = 38.5%
    • Loops tied and corners tucked back in = 60.3%
    • Secured with ear guard = 61.7%
    • Secured with 23-mm claw-style hair clip = 64.8%
    • Secured with 3 rubber bands to fix the mask = 78.2%
    • Secured with a 10-inch segment of nylon hosiery = 80.2%

Clinical Implications

  • In a previous study by Sickbert-Bennett and colleagues, expired or sterilized N95 respirators retained greater filtering efficiency vs other types of masks for particles similar in size to SARS-CoV-2.
  • In the current study by Clapp and colleagues, the most effective mask outside of N95 respirators for the prevention of possible COVID-19 was the 2-layer nylon mask with ear loops and an aluminum nose bridge, provided that the mask had been washed once. Wearing a segment of nylon hosiery over a typical medical procedure mask was the most effective augmentation of such a mask.
  • Implications for the healthcare team:  The healthcare team can recommend masks for patients according to the current study, and the team can also employ these findings routinely in their daily lives to protect themselves and the community from COVID-19.

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