The Centers for Disease Control and Prevention (CDC) unveiled new guidance Tuesday recommending all students in grades K-12 wear masks even if they’re fully vaccinated.

Previously, the CDC recommended masks indoors for students not yet fully vaccinated. This included anyone under the age of 12, as this age group is not yet eligible to get the vaccine. The CDC changed its guidance on Tuesday as the Delta variant – believed to be more transmissible – spikes across the country.

“This includes schools,” CDC director Dr. Rochelle Walensky said Tuesday after noting new guidelines on vaccinated adults masking up in certain circumstance. “CDC recommends that everyone in K-12 schools wear a mask indoors, including teachers, staff, students and visitors, regardless of vaccination status. Children should return to full-time, in-person learning in the fall with proper prevention strategies in place.”

Walensky explained that the CDC’s previous school guidance, released on July 9, came at a time when the Delta variant was less prevalent. She said the CDC was “really hopeful that we’d have more people vaccinated” and cited the low percentage of vaccinations among the 12-17 years-old age group as reason for the blanket rule.

“I think we all agree than children … 11 and less are not going to be able to be vaccinated, and with only 30% of our kids between 12 and 17 fully vaccinated now, more cases in this country and a real effort to try and make sure that our kids can safely get back to full, in-person learning in the fall, we’re recommending that everybody wear masks right now.”

President Joe Biden predicted during CNN’s town hall last week that those under 12 can probably get vaccinated “soon.” He also suggested the CDC’s new guidelines would tell those in that age group to mask up at school until vaccinated. Walensky didn’t go into depth on when the country can expect the vaccine to be approved for children.

“The CDC is going to say that what you should do is everyone under the age of 12 should probably be wearing masks in school. That’s probably what’s going to happen,” Biden said last week after a Democratic attendee asked what his message for parents and educators are as they work on reopening schools. “Secondly, those over the age of 12 who are able to get vaccinated, if you’re vaccinated you shouldn’t wear a mask. If you aren’t vaccinated, you should be wearing a mask.”

The CDC’s guidelines have taken Biden’s prediction a step further by issuing a mass mask recommendation for all students regardless of vaccination status. (RELATED: ‘The Choice Is Yours’: In Line With CDC’s Mask Guidance, Biden Gives Americans An Ultimatum On Vaccines)

The guidelines also come despite reports that children often don’t become as sick as adults from the virus and appear to be at lower risk of contracting it.

“While all children are capable of getting the virus that causes COVID-19, they don’t become sick as often as adults. Most children have mild symptoms or no symptoms,” the Mayo Clinic reported. “According to the American Academy of Pediatrics and the Children’s Hospital Association, in the U.S. children represent about 13% of all COVID-19 cases. Research suggests that children younger than ages 10 to 14 are less likely to become infected with the virus that causes COVID-19 compared to people age 20 and older.”

Still, as the Mayo Clinic noted, “some children” do become very sick from the virus, particularly those with underlying conditions. Overall, however, the children are at an “extremely low risk,” the BBC reported in July, citing a study from scientists from University College London and the Universities of York, Bristol and Liverpool.

“Children are at extremely slim risk of dying from Covid-19, according to some of the most comprehensive studies to date, which indicate the threat might be even lower than previously thought,” The Wall Street Journal also noted.