a New Research Lancet Face coverings have been shown to significantly reduce the amount of SARS-CoV-2 in an infected person’s breath, by up to 98 percent, depending on the type of face covering worn.
This study is the first to measure viral shedding in infected humans with and without face coverings in a realistic setting where masks and respirators are used. Previous studies have only used mannequins. Volunteers who participated in the study were not trained or provided with fit testing or extensive instructions on how to use masks or respirators to best limit virus spread.
Registered nurse Diane Miller dons an N-95 mask and heads to a patient’s room as she enters the “red zone” of the COVID Acute Care Unit at the University of Washington Medical Center-Montlake in Seattle, Tuesday, Jan. 26, 2021. [AP Photo/Elaine Thompson]
The end result is that this study fairly accurately replicates real-world conditions of face covering selection and use, and the measured viral load reductions represent what one could realistically expect without significant efforts to fit, test, and train the entire population on proper use.
Another important strength of this study is that we directly measured the amount of virus in the breath of the same subjects at the same time, with and without a face covering, so each subject served as his or her own control. Moreover, capturing the virus in the breath allowed us to determine the specific strain of virus that subjects were infected with.
The study enrolled 106 volunteers between June 2020 and May 2022. Of these, 44 provided 60 same-day samples, one with and one without a face covering, of which at least one had detectable levels of SARS-CoV-2 virus.
The face coverings examined in the study were N95 and KN95 respirators as well as cloth and surgical masks. Study volunteers were randomly assigned to wear cloth masks or bring their own cloth masks. The majority of the KN95 respirators tested were provided to students and employees by the University of Maryland (where the study took place). The surgical masks and N95 respirators tested were also provided to volunteers, so most were one brand of device.
The study evolved over time from comparing cloth masks to surgical masks to comparing KN95 masks to surgical masks to KN95 masks to N95 masks. Of the 60 total paired samples, 8 were made with cloth masks, 26 with surgical masks, 13 with KN95 masks, and 13 with N95 masks.
The authors had previously published the results of this study. Lancet For the first time, results for N95s and nearly all KN95s are included.
