N95 Respirators Provide Superior Source Control for SARS-CoV-2

JIANYU LAI, Kristen K. Coleman, Sheldon Tai, Jennifer German, Filbert Hong, Barbara J. Albert, Yi Esparza, Aditya Kiran Srikakulapu, Petri Kalliomäki, Maria Schanz, Isabel Sierra Maldonado, Molly Oertel, Naja Fadul, Louie Gold, Kathleen McPhaul, Tianzhou Ma, Benjamin Cowling, Donald K. Milton, School of Public Health, University of Maryland, College Pk

     Abstract Number: 570
     Working Group: Aerosol Science of Infectious Diseases: Lessons and Open Questions on Models, Transmission and Mitigation

Abstract
BACKGROUND: SARS-CoV-2 is transmitted by infectious aerosols. Face masks reduce viral exhaled breath aerosols (EBA) released by infected persons. No human study has yet compared the efficacy of different masks and respirators as source controls. Here, we compared the efficacy of cloth masks, surgical masks, KN95, and N95 respirators as source control for SARS-CoV-2.

METHODS: From June 2020 to May 2022, volunteers infected with SARS-CoV-2 provided paired 30-minute EBA samples while masked and unmasked, using a Gesundheit-II sampler. Volunteers received no official training in the proper use of respirators. Our analysis included paired masked-unmasked same-day samples with detectable SARS-CoV-2 RNA. Aerosols were categorized by size: fine (≤5 μm) and coarse (>5 μm). Linear mixed effect models with censored responses were used to model the effect of masks on EBA viral RNA load, controlling for number of coughs during sampling and nested random effects of subjects.

RESULTS: Forty-four volunteers (3 Alpha, 2 Delta, 21 Omicron, and 18 Others) provided 60 same-day paired samples. All mask types significantly reduced the viral RNA load in both aerosol size fractions. N95 respirators reduced fine and coarse aerosol viral RNA by 98% (95% CI: 96% to 99%) and 99% (95% CI: 96% to 100%), respectively, and significantly outperformed face masks and KN95 respirators (p<0.05). We observed no significant difference among face masks and KN95 respirators.

CONCLUSIONS: Masks work as source control for SARS-CoV-2 and are appropriate for general community use to reduce transmission. N95 respirators are significantly more effective than all other types of masks even when used by untrained study participants. N95 respirators should be the standard of care in nursing homes and healthcare settings for both personal protection and source control when respiratory viral infections are prevalent in the community and healthcare associated transmission risk is elevated.

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