However, millions of Americans no longer need to do so, according to new guidance that includes federal COVID-19 data from hospital.

As cases dropped in the wake Omicron variant wave, the agency’s recommendations are now more widely accepted. These changes are one of the biggest shifts in COVID-19 guidance since last January when the CDC stated that all Americans should wear masks indoors if they live in areas deemed to have “substantial” or high levels of transmission.

According to the new framework of the CDC, masks are no longer necessary indoors for Americans living in areas with low levels of the disease. If they are at high risk for severe diseases, such as those with compromised immune systems, residents of counties that have a “medium” level of risk should wear masks. Residents of counties with a high risk — approximately 28.2% of Americans — need to still wear masks indoors.

Greta Massetti, CDC’s Greta, said Friday that communities can use these metrics along with their own local metrics such as wastewater surveillance and emergency department visits and workforce capacity to update and further inform local policies.

Although the daily pace for new cases has slowed to more than 90% nationally since the peak Omicron wave last week, the vast majority had remained in the “high” transmission zone according to the original COVID-19 metrics.

These thresholds are from the first year of the pandemic. They were before vaccines and prior infections. Growing supplies of effective treatments reduced the severity of the threat.

“The overall risk of severe diseases is generally lower now that there is widespread immunity in the population. As the virus continues its spread in our communities, it is important that we focus our metrics beyond cases and instead direct our efforts towards protecting those at highest risk of severe illness and preventing COVID-19 overloading our hospitals,” Dr. Rochelle Walensky, CDC Director, said.

Massetti and Walensky said that the new benchmarks would be updated on a weekly basis, county-by-county. They place more emphasis on the number of hospitalizations per community than the number of infections. The presentation outlines the agency’s analysis and concluded that the new formula has “higher deaths rates” in the future than their previous benchmarks.

From the Omicron wave record, the average number of COVID-19 hospital patients has dropped more than 60%. According to agency studies, patients are less likely to be hospitalized if they have Omicron than those with the Delta variant.

Many areas of the country had already taken steps to relax their mask rules before the CDC’s new guidance. These included lifting statewide mandates and rolling back rules at schools. This was based on similar assessments regarding the disease’s danger.

“Omicron was a game-changer, when it wasn’t just about how many cases you had in a particular community, but also about what the severity was of disease,” Dr. Umair Shah, Washington’s secretary for health, said in an interview before the final guidance was published.

Washington announced earlier this month plans to remove indoor mask requirements for March. Shah stated that the CDC held “ongoing conversations” with state health officials as they drafted new metrics. However, Shah did not share the final details of how their guidance would balance recommendations for vulnerable people in situations such as schools and workplaces.

“We are the ones that have to interpret and implement the guidance. The CDC has made multiple attempts to meet with state health officials and held ongoing discussions to find out what the future holds. Shah said.

Although the agency stated that its COVID-19 metrics would “inform” new recommendations and be used indoors in places such as schools, it did not provide details about how other aspects of its guidance might be modified.

The CDC announced Friday afternoon that it would lift the federal school bus mask requirement. However, rules for other travel parts, such as airports, train stations and trains, will continue to be in place until at least next month. The CDC stated that guidance for nursing homes and hospitals will remain based on the agency’s old community transmission thresholds.

Although the agency stated that their COVID-19 metrics would “inform” new recommendations it did not provide details about how specific agency guidance might be changed. Masks are still required in schools and airports in areas with “high” disease levels.

The federal health officials claim that they sought out a wide range of experts and local officials to help them formulate their new recommendations. This comes amid a bigger effort “COVIDNext” to review their surveillance strategies in order to be “appropriate to this stage of the pandemic.”

A coalition of public and non-profit health organizations declared last month they supported ending widespread COVID-19 contact tracer use, as some states and counties health authorities have done, in return for “a more strategic approach to outbreak investigations and targeted cases investigations.”

The CDC is promoting efforts to increase alternative methods to monitor trends in the disease. For example, they are testing sewage to determine levels of the virus. But not all communities have access to this data.

“We assessed all data sources against several criteria. These included how well they could measure severe disease and healthcare strain. What extent do they offer data at the local level that can be used to inform local decisions? Massetti said.

Federal health officials warn that COVID metrics that are rapidly declining could be reversed if there are new forms of concern.

BA.2, an Omicron sub-lineage, has gradually grown to make up about 4% of new infection in the U.S.

Although international health officials state that there is no evidence that BA.2 causes more severe infections than others, data from many countries suggests it could spread quicker. The Food and Drug Administration also asked if at least one monoclonal antibody drug that is currently in use will be effective against the subvariant.

Walensky stated that he wanted to give people a break with mask wearing during low levels and to then be able to reach for them again should the situation worsen.