WASHINGTON, Jan 14 (Reuters) – The U.S. Centers for Disease Control and Prevention (CDC) on Friday revised its guidance for Americans on wearing masks to protect against COVID-19, recommending donning “the most protective mask you can” while stopping short of advocating nationwide usage of N95 respirators.

The CDC, an agency critics have accused of offering shifting and confusing guidance amid the pandemic, clarified on its website “that people can choose respirators such as N95s and KN95s, including removing concerns related to supply shortages for N95s.”

Americans should “wear the most protective mask you can that fits well and that you will wear consistently,” the CDC added.

The United States leads the world in COVID-19 deaths – roughly 850,000 – even as it battles a surge of cases involving the fast-spreading Omicron coronavirus variant. Complicating matters is the refusal of some Americans to get vaccinated.

President Joe Biden said on Thursday that the federal government plans to make “high-quality masks” available to Americans for free. In another step, the White House on Friday said the government will begin shipping 500 million COVID-19 tests to Americans later this month without charge.

The CDC said it wants to encourage Americans to wear masks rather than push them to wear the highest-grade face protection, but also explicitly said that respirators provide the best level of protection. It said that “loosely woven cloth products provide the least protection.”

“Masking is a critical public health tool to prevent the spread of COVID-19, and it is important to remember that any mask is better than no mask,” the CDC added.

The CDC said the revised recommendations “reflect the science on masking, including what we have learned in the past two years,” since the start of the pandemic.

More Americans have been recently opting for higher-grade protection amid the surge in cases.

The United States is tallying about 1,800 COVID-19 deaths and 780,000 new infections daily – the most in the world – as well as record levels of hospitalized patients.

The Omicron-related surge appears to be slowing in areas that were hit first, including states in the Northeast and South, according to a Reuters analysis. In Western states, the number of new cases climbed 89% in the past week compared with the previous week.

The CDC last May announced that fully vaccinated people could shed their face coverings, as COVID-19 cases were then on the decline. But in July, the CDC said fully vaccinated people should wear masks in indoor public places in regions where COVID-19 was spreading rapidly. The CDC said this week 99.5% of U.S. counties currently are covered by the mask recommendation.

Some U.S. N95 makers told Reuters they had record N95 sales after Anthony Fauci, Biden’s chief medical adviser, recommended on CNN that Americans “get the highest quality mask that you can tolerate and that’s available to you.”

N95 masks that are worn correctly will filter out at least 95% of particulate matter in the air, preventing anything larger than 0.3 micron from passing through.

Los Angeles County, the nation’s most populous, on Monday will require some employers to provide “medical-grade” masks – surgical masks, KF94, KN95s or N95s – to workers at high risk of contracting a COVID-19 infection on the job.

Masks remain polarizing. Biden, a Democrat, this week again urged people to wear masks and noted that about a third of Americans report they do not wear a mask at all. Many Republican-leaning states have no mask requirements. Some Democratic-governed states such as California have reimposed indoor mask mandates.

Blair Childs, an executive at Premier Inc (PINC.O), a group-purchasing company for hospitals, expressed concern about legislation backed by U.S. Senator Bernie Sanders that would send every person in the country a pack of three N95 masks. Childs said such proposals could “throw the healthcare supply chain into disarray.”

Days after taking office in January 2021, Biden imposed mask requirements on airplanes, trains and public transit and in airports and other transit hubs – actions his predecessor Donald Trump declined to take. Biden last month extended the transit mask requirements through March 18. The CDC on Friday said N95 masks may be considered for use in places like transit “when greater protection is needed or desired.”

Reporting by David Shepardson in Washington; Additional reporting by Lisa Baertlein in Los Angeles; Editing by Will Dunham, David Gregorio and Matthew Lewis

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