Updated criteria to guide COVID-19 restrictions will be announced by the U.S. Centers for Disease Control and Prevention later this week or early next week, according to a CDC scientist involved in the process.

Currently, the agency's guidance on measures such as mask use and social distancing is based on the number of new cases per 100,000 people and the percent of positive tests in the past seven days.

Guidance will soon be based on COVID-19 levels in an individual county, the CDC scientist told CNN.

"There will be consideration that when you get to this level, you'll want to consider doing this; when you get to this level, you want to consider doing this," the source said. "Hopefully, they'll be stressing the importance of local health departments making decisions according to local circumstances."

Based on current criteria, 97% of counties are at substantial or high transmission, but the updated criteria will place fewer counties at the highest levels of transmission, according to the scientist.

There are two reasons for the criteria change — many more people are vaccinated now and the dominant omicron variant causes much milder illness, the source told CNN.

Instead of looking at local cases alone, the CDC wants to give more emphasis to meaningful consequences such as hospitalizations, emergency room visits and deaths, which is similar to how the agency monitors influenza, according to the scientist.

"Meaningful consequences of the illnesses give us a better impact of COVID on people and the health care system," the source told CNN. "This has been something folks have been engaged with and working on very hard — I mean really hard — over the past few weeks. It started before omicron, and then omicron pulled everyone into it, and now we'll be able to finish it."

Several states have already announced changes to their COVID restrictions and some governors have asked the CDC for clearer guidance about how to make such decisions, CNN reported.