CDC Research: Double Masking Can Reduce COVID-19 Transmission & Exposer by up to 96.4%

A new research report published by the Centers for Disease Control and Prevention (CDC) has found that wearing a tight-fitting surgical mask, or doubling up on masks (wearing a cloth mask over a medical/surgical mask), can significantly reduce COVID-19 transmission and slow the spread of new, more contagious strains of COVID-19 .

Universal masking is recommended to slow the spread of COVID-19. Cloth masks and medical procedure masks substantially reduce exposure from infected wearers (source control) and reduce exposure of uninfected wearers (wearer exposure).

Note: However, ensuring that these masks fit properly is key in order to prevent air from leaking around the edges.

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CDC Reports on double masking:

Investigators tried 2 approaches: layering a cloth mask over a medical mask and wearing a medical mask with knotted ear loops and tucked-in sides.

CDC conducted experiments to assess 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. Each modification substantially improved source control and reduced wearer exposure.

· The study results suggest that when fitters are secured over a medical mask, they can increase the wearer’s protection by 90% or more for aerosols in the size range considered being the most important for transmitting SARS-CoV-2, according to the CDC.

· Double masking is another method to improve the fit of medical masks while maximizing the filtration properties of the materials they are constructed from.

Findings:

They found that;

A double-masked source reduced exposure to an unmasked receiver by 82.2%
A knotted-and-tucked-masked source reduced exposure to an unmasked receiver by 62.9%
An unmasked source but double-masked receiver reduced exposure by 83%
An unmasked source but knotted-and-tucked-masked received reduced exposure by 64.5%
A double-masked source reduced exposure to a double-masked receiver by 96.4%
A knotted-and-tucked-masked source reduced exposure to a knotted-and-tucked-masked receiver by 95.9%

CDC recommendations on mask wearing:

To ensure proper mask-wearing, the CDC recommendations include:

Choosing a mask that has two or more layers of washable, breathable fabric
Putting the mask over the nose and mouth and securing it under your chin
Knotting the ear loops of a surgical mask, where they attach to the mask, and then tucking in and flattening the extra material close to the face (knotted and tucked masks)
Fitting the mask snugly against the sides of the face, and slipping the loops over the ears or tying the strings behind the head

What are the implications for public health?

These experiments highlight the importance of good fit to maximize mask performance. There are multiple simple ways to achieve better fit of masks to more effectively slow the spread of COVID-19.