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CDC director clarifies why isolation guidance changed from 10 days to 5

Rochelle Walensky addressed confusion over the CDC’s changing guidelines released last week. “We are now standing on the shoulders of years of science," she said.

The director of the Centers for Disease Control and Prevention explained why the agency has shortened its recommended isolation period for people infected with COVID-19, saying it's based on "years of science" about when people are most contagious with the virus.

Rochelle Walensky spoke on TODAY Friday amid confusion over the CDC's changing guidelines released last week. The CDC now recommends an isolation period of five days for infected people who do not have symptoms or whose symptoms are lessening, compared to the previous recommendation of a 10-day isolation period.

The CDC also now does not recommend testing before leaving isolation, a change that has drawn criticism from some medical experts. The American Medical Association rebuked the CDC this week, saying the guidelines are confusing and counterproductive, and risk spreading the virus further.

Walensky defended the changes.

"We are now standing on the shoulders of years of science that has demonstrated that if you are infected, you are most contagious in the one to two days prior to your symptoms and the two to three days after your symptoms," Walensky told Savannah Guthrie. "So we know that the vast majority of your contagiousness by day five is really behind you.

"So in this moment where we’re evaluating the science and looking at the epidemiology of the disease, we said five days of isolation and then, are you feeling better? Is your cough gone? If your symptoms are gone, we say you’re OK to come out of that isolation, but you really do need to wear a mask all of the time."

Walensky framed getting tested at the end of the isolation period as a choice rather than a recommendation. The CDC has also issued guidance for how to interpret a test "if you choose to take that step at the end of your isolation," according to Walensky.

Memes have popped up on Twitter mocking the CDC's changing guidance with the phrase, "The CDC recommends..." Walensky addressed the issue of the agency's credibility.

"We at the CDC are 12,000 people who are working 24-7 following the science with an ever-evolving nature in the midst of a really fast-moving pandemic, and we are doing so, putting our head down, to keep America safe," Walensky said. "We will continue to update, we will continue to improve how we communicate to the American public. This is fast-moving science."

As COVID-19 cases of the omicron variant continue to surge across the country, school districts are grappling with whether to continue in-person learning or go remote. Chicago public schools have been closed to in-person learning for two straight days after the teachers union voted to switch back to remote learning during the surge.

Walensky advocated for schools to remain open to in-person learning.

"I want to remind people that we had a delta surge in the fall, and we were able to successfully keep our schools safely open, and we did that even before we had vaccines for our children," Walensky said.

She recommended children 5 to 11 and 12 to 17 get vaccinated, and for schools to continue to use tools like masks, test-to-stay strategies, and the new recommendation for decreased isolation time so teachers can return to school more quickly after an infection.