By Elizabeth Cohen and Jacqueline Howard, CNN

(CNN) -- Most people in the United States live in areas where those who are healthy do not need to wear masks indoors, according to new US Centers for Disease Control and Prevention guidance -- a sweeping change from what earlier Covid-19 metrics recommended.

New CDC metrics indicate that about 28% of people in the United States live in a county where they need to wear masks indoors. Previously, CDC pointed to levels of coronavirus transmission within communities as a key metric for restrictions and recommended that people in areas with high or substantial levels of transmission -- about 99% of the population -- should wear masks indoors.

Now, the CDC's "Covid-19 community level" metrics are based on three pieces of data in a community: new Covid-19 hospitalizations, hospital capacity and new Covid-19 cases. The CDC's website includes a list of US counties and their current Covid-19 levels.

Under the updated guidance, more than 70% of the US population is in a location with low or medium Covid-19 community levels. For those areas, there is no recommendation for indoor masking unless you are at potential "increased risk" for Covid-19 and if so, the CDC recommends to talk to your health care provider about wearing a mask.

At all levels, the CDC recommends people get vaccinated and boosted, and get tested if they have symptoms.

In areas with "high" levels, the CDC also advises wearing a mask in public indoor settings, including schools. In areas with "medium" levels, the CDC advises talking with your doctor about wearing a mask if you're at increased risk for Covid-19. In areas with "low" Covid-19 community levels, there is no recommendation for mask wearing.

The CDC notes that anyone who wants to wear a mask should continue to do so.

"This new framework moves beyond just looking at cases and test positivity, to evaluate factors that reflect the severity of disease -- including hospitalizations and hospital capacity -- and helps to determine whether the level of Covid-19 and severe disease are low, medium or high in a community," CDC Director Dr. Rochelle Walensky told reporters during a telebriefing call Friday.

"The Covid-19 community level we are releasing today will inform CDC recommendations on prevention measures, like masking, and CDC recommendations for layered prevention measures will depend on the Covid-19 level in the community," Walensky said. "This updated approach focuses on directing our prevention efforts towards protecting people at high risk for severe illness and preventing hospitals and health care systems from being overwhelmed."

Community Covid-19 levels

Counties with fewer than 200 new Covid-19 cases per 100,000 people in the past week are considered to have "low" Covid-19 community levels if they have fewer than 10 new Covid-19 hospital admissions per 100,000 or less than 10% of staffed hospital beds occupied by Covid-19 patients on average in the past week.

Levels are "medium" if counties have 10 to nearly 20 new Covid-19 hospital admissions per 100,000 or between 10% and 14.9% of staffed hospital beds occupied by Covid-19 patients on average in the past week.

Levels are considered "high" if counties have 20 or more new Covid-19 hospital admissions per 100,000 or at least 15% of staffed hospital beds occupied by Covid-19 patients on average in the past week.

Counties with 200 or more new Covid-19 cases per 100,000 people in the past week are not considered to have "low" levels of Covid-19. They are considered "medium" if they have fewer than 10 new Covid-19 hospital admissions per 100,000 or less than 10% of staffed hospital beds occupied by Covid-19 patients on average in the past week. They are considered "high" if they have if they have 10 or more new Covid-19 hospital admissions per 100,000 or at least 10% of staffed hospital beds occupied by Covid-19 patients on average in the past week.

The update to CDC guidance comes at a time when daily Covid-19 cases in the United States have fallen to a tenth of what they were at their peak last month, according to data from Johns Hopkins University. The 90% drop -- from an average of more than 802,000 cases per day on January 15 to less than 75,000 currently -- happened over the course of about six weeks.

In recent weeks, some states seem to have already made this shift in focus from community transmission to hospitalizations. Many states have made plans to lift indoor or school mask mandates based on their own metrics: declining hospitalization rates and having a larger share of fully vaccinated residents than the national average.

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