The Centers for Disease Control and Prevention conceded Friday that cloth masks are less effective than surgical or respirator masks as protection against COVID-19 .

The updated guidance reflects what many public health experts have emphasized throughout the recent surge in cases driven by the highly transmissible omicron variant.

Loosely woven cloth products provide the least protection, layered finely woven products offer more protection, well-fitting disposable surgical masks and KN95s offer even more protection, and well-fitting NIOSH-approved respirators (including N95s) offer the highest level of protection, according to the new guidance issued Friday.

But the CDC didnt go so far as to say cloth masks are inadequate against this strain of the virus something some public health experts say is apparent given the transmission rates. Instead, the new guidance says respirator masks, such as N95 or KN95 masks, may be considered in certain situations and by certain people when greater protection is needed or desired. That may include scenarios involving infected patients or people with co-morbidities, or when social distancing is not possible, the CDC said.

Its a shift from earlier in the pandemic when the CDC, concerned about a scarcity of protective equipment, urged people to spare such respirator masks for health care workers.

N95 and KN95 masks filter at least 95% of airborne particles, and recent data shows they may protect wearers against omicron-infected, unmasked people for up to 2, compared with just 20 to 30 minutes of protection from cloth or surgical masks.

Sen. Bernie Sanders (I-Vt.) is spearheading an effort to send every American three free N95 masks in light of that data.

It is an absolute scandal that in the richest country in the history of the world, high-quality masks are not more readily available to frontline workers, health care workers and all Americans, Sanders said Wednesday when he introduced the Masks for All Act.