The Centers for Disease Control and Prevention (CDC) said Tuesday that fully vaccinated individuals should wear masks in certain indoor areas and advised universal masking for schools regardless of individuals' vaccination status amid rising infections due to the delta variant. CDC Director Dr. Rochelle Walensky later said in a call with reporters that the decision to issue new guidance "was not something we took lightly," but comes amid "worrisome" new science. 

"In recent days, I have seen new scientific data from sequenced outbreak investigations showing that the delta variant behaves uniquely differently from past strains of the virus that cause COVID-19," Walensky told reporters over a call. "Information on the delta variant from several states and other countries indicate that 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," Walensky said.

Walensky noted that vaccinated individuals represent a small percentage of new virus transmission and that the agency continues "to estimate the risk of a breakthrough infection with symptoms upon exposure to the delta variant is reduced by seven-fold." 

"The reduction is 20-fold for hospitalizations and deaths," she said. "As CDC has recommended for months, unvaccinated individuals should get vaccinated and continue masking until they are fully vaccinated." 

Per the new guidance, in areas with substantial and high transmission, CDC recommends that fully vaccinated individuals wear a mask in public indoor settings to help prevent spread of delta and protect others.


"This moment, and most importantly, the associated illness, suffering and death could have been avoided with higher vaccination coverage in this country," she said. 

In a significant shift from prior guidance, the CDC also recommended "universal indoor masking for all teachers, staff, students, and visitors to K-12 schools, regardless of vaccination status." 

Walensky sidestepped whether the new guidance would remove the incentive for some parents to seek vaccines for kids.

The CDC previously advised masks be worn indoors by all individuals ages 2 and older not fully vaccinated against coronavirus and stated that those who are fully vaccinated didn’t need to wear a mask or physically distance in any setting, including while participating in extracurricular activities or while eating. However, the agency noted that based on the needs of the community, a school may opt to make mask use universally required regardless of vaccination status. 

Walensky later stated that the CDC's decision to issue new guidance was "not something we took lightly." 

"This new data weighs heavily on me, this new guidance weighs heavily on me," she said. "And I just wanted to convey that this is not a decision that was taken lightly."


The CDC urged those not yet vaccinated, and eligible to receive a COVID-19 vaccine, to do so, writing: "Unvaccinated individuals should get vaccinated and continue masking until they are fully vaccinated. With the Delta variant, this is more urgent than ever. The highest spread of cases and severe outcomes is happening in places with low vaccination rates and among unvaccinated people."

The CDC defines areas of substantial viral transmission as 50 to 100 cases per 100,000 population over a seven-day period, and high viral spread is defined as over 100 cases per 100,000 over a seven-day period. Some areas are experiencing over 300 cases per 100,000 population at the moment, Walensky said.

Fox News' Alexandria Hein contributed to this report.