During the first several months of the pandemic, health experts discouraged the general public from buying N95 masks, since medical professionals were facing a shortage of personal protection equipment. But it has “been many months since supply of N95s (has been) an issue,” Wen said.

Yet the US Centers for Disease Control and Prevention’s most recent guidance on selecting, properly wearing, cleaning and storing face masks recommended people avoid N95 masks and instead choose masks with two or more layers of washable, breathable fabric — which Wen called “a major mistake.”

“If we’re going to go as far as to say that masks are required — when we don’t come from a mask-wearing culture and people don’t like wearing masks — at least recommend that they wear the most effective mask,” Wen said.

Other countries, including Germany and Austria, have “switched their standard to say that a face covering in public must be at least a medical-grade surgical mask” in certain settings, she added.