Dr. Anthony Fauci, President Biden’s chief medical adviser on COVID-19, said two face masks are likely more effective than one against the novel coronavirus, despite significant uncertainty on the subject.
"If you have a physical covering with one layer, you put another layer on it just makes common sense that it likely would be more effective," Fauci told NBC News on Monday.
Infectious disease experts from Stanford Health Care, Mayo Clinic and Johns Hopkins University recently told Fox News there is little to no evidence on the issue.
Neysa Ernst from Johns Hopkins University, where she serves as nurse manager of the Biocontainment Unit, agreed, though she proposed that anecdotal evidence suggests additional layers could offer "psychological safety" to some.
"In this pandemic psychological safety is important, it provides a sense of control in an unknown environment," Ernst wrote.
According to the Centers for Disease Control and Prevention (CDC), masks should have two layers of breathable fabric, with a snug fit covering the nose and mouth.
There is some conflicting advice on double-masking, which suggests there isn’t enough research behind it yet. When worn correctly, a single face mask made of "appropriate material" typically offers enough protection, Paula Cannon, a distinguished professor of molecular microbiology and immunology at the Keck School of Medicine of University of Southern California (USC), previously said in an email.
"However, wearing two can provide additional protection. A second mask can create a tighter seal around your face, and also help secure the masks so they don’t slip down," she added.
Another physician, Dr. Dave Hnida, previously told CBS that two masks can create more of an "obstacle course" for viral particles in an attempted route from the air, through the body and into the lungs.