U.S. health officials on Friday encouraged more Americans to wear the kind of N95 or KN95 masks used by health-care workers to slow the spread of the coronavirus.

Those kinds of masks are considered better at filtering the air. But they were in short supply previously, and Centers for Disease Control and Prevention officials had said they should be prioritized for health care workers. 

In updated guidance posted late Friday afternoon, CDC officials removed concerns related to supply shortages and more clearly said that properly fitted N95 and KN95 masks offer the most protection. 

However, agency officials noted some masks are harder to tolerate than others, and urged people to choose good-fitting masks that they will wear consistently.

“Our main message continues to be that any mask is better than no mask,” Kristen Nordlund, a CDC spokeswoman, said in a statement.

The CDC has evolved its mask guidance throughout the pandemic. 

In its last update, in September, CDC officials became more encouraging of disposable N95 masks, saying they could be used in certain situations if supplies were available. Examples included being near a lot of people for extended periods of time on a train, bus or airplane; taking care of someone in poor health; or being more susceptible to severe illness.

On Thursday, President Joe Biden announced that his administration was planning to make “high-quality masks,” including N95s, available for free. He said more details were coming next week. The federal government has a stockpile of more than 750 million N95 masks, the White House said.

The latest CDC guidance notes that there is a special category of “surgical N95” masks, that are specially designed for protection against blood splashes and other operating room hazards. Those are not generally available for sale to the public, and should continue to be reserved for health care workers, the agency said.