'New science is worrisome': CDC recommends wearing masks indoors, again. What that means for vaccinated Americans.

The CDC's decision Tuesday to reverse course and urge even fully vaccinated Americans to wear masks indoors in areas of high coronavirus transmission isn't likely to crush community spread, experts say – but it might ratchet up pressure on the unvaccinated and encourage businesses and schools to implement mask mandates.

The CDC is also now recommending universal indoor masking for all teachers, staff, students and visitors inside schools from kindergarten to 12th grade, regardless of vaccination status. That aligns closely with guidelines from the American Academy of Pediatrics, which recommended this month that anyone older than 2 be required to wear a mask in school.

The CDC and the AAP are still urging that children return to full-time in-person learning in the fall.

"The delta variant is showing every day its willingness to outsmart us and be an opportunist," CDC director Dr. Rochelle Walensky said in a briefing Tuesday. "In rare occasions, some vaccinated people infected with the delta variant after vaccination may be contagious and spread the virus to others. ... This new science is worrisome and unfortunately warrants an update to our recommendations."

According to the new science, she said, fully vaccinated people with breakthrough infections from the delta variant have a similar viral load to infections in unvaccinated people. That means the fully vaccinated are more likely to spread the virus with the delta variant than the original coronavirus.

"If you have a vaccinated individual who is in a place with substantial or high transmission – and they're contacting a lot of people – 1 in 20 or 1 in 10 could possibly lead to a breakthrough infection" even with a vaccine that's 90 to 95% effective," Walensky said.

The goal behind the guidance may be to protect both the fully vaccinated and the unvaccinated, health experts say, especially vaccinated people who may be immunocompromised and children under 12 who aren’t yet eligible to get their shot.

But the reality is there’s hardly any transmission among fully vaccinated people to truly affect community spread, they say.

“There isn’t a whole lot of benefit that’s going to be felt by this. … We have good data that vaccinated people don’t spread COVID as efficiently as unvaccinated people,” Dr. Eric Cioe-Peña, director of global health at Northwell Health in New Hyde Park, New York, told USA TODAY.

He suspects the new recommendations may be more successful in getting unvaccinated Americans to wear masks in public and empowering businesses and schools to implement mask mandates without requiring proof of vaccination.

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The CDC’s recommendations now also align more closely with local health departments that already have reimposed mask mandates because of rising coronavirus cases, said Dr. William Schaffner, a professor and infectious disease expert at the Vanderbilt University School of Medicine in Nashville, Tennessee.

“This gives more of an opportunity for local health departments to not look as though they’re doing something different than what the CDC is suggesting,” he said. “There was always an option for locals to make that determination, but now it’s much more explicit.”

The CDC’s announcement comes a few days after Dr. Anthony Fauci, President Biden’s chief COVID-19 medical adviser, said the agency was reexamining mask recommendations amid surging cases triggered by the highly transmissible delta variant.

“We’re going in the wrong direction,” he told CNN on Sunday.

The delta variant accounts for more than 80% of COVID-19 cases across the United States, according to the CDC.

Johns Hopkins University data shows daily cases are nearly doubled what they were last summer, and wearing a mask is an extra layer of protection to prevent another fall surge, said Dr. Ilan Shapiro, medical director of health education and wellness at AltaMed Health Services, a Los Angeles network of community health centers.

“We already know how that movie ends,” he said. “Right now, we’re trying to protect every human being that we have around us (regardless of vaccination status), as the delta variant has proven to us that it’s a very effective jumper.”

Health experts urge fully vaccinated people to consult their local health department websites for mask guidance and vaccination rates. If rates are below 70%, they recommend wearing a face covering in indoor public places or crowded outdoor gatherings.

The No. 1 recommendation, however, will always to be to get vaccinated, Cioe-Peña said.

“We have the tools and we’re one of the only countries in the world that can end the pandemic, and we’re just choosing not to,” he said. “We’re choosing to extend our pandemic, and that’s frustrating.”

For those who are already vaccinated, Schaffner urges them to be flexible and patient as CDC recommendations are likely to change again with fluctuating vaccination rates and coronavirus transmission.

“The virus is in charge, and we have to respond to what the virus is doing in our communities,” he said. “Some people would think of that as a step back, but when the opposing team makes a lot of points, you have to change your defense.”

Follow Adrianna Rodriguez on Twitter: @AdriannaUSAT.

Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.

This article originally appeared on USA TODAY: COVID-19: Why CDC wants vaccinated Americans to wear masks again