The Centers for Disease Control and Prevention is recommending all individuals—including fully vaccinated individuals—wear masks in K-12 schools.

Additionally, the updated CDC guidance recommends fully vaccinated people in areas with "high" or "substantial" levels of transmission wear masks in indoor, public settings.

Substantial transmission is defined by the CDC as 50-99.99 new COVID-19 cases per 100,000 people in the past seven days, while high transmission is 100 or more new cases per 100,000 in the past seven days. According to the CDC's COVID-19 data tracker, more than 63% of all counties nationwide—including many in Texas—have high or substantial transmission.

CDC Director Dr. Rochelle Walensky announced the new masking recommendations during a July 27 press conference.

"Today, we have new science related to the delta variant that requires us to update the guidance regarding what you can do when you are fully vaccinated," Walensky said. "The delta variant is showing every day its willingness to outsmart and to be an opportunist in areas where we have not shown a fortified response against it."

Walensky said the change in guidance was prompted by recent data that shows fully vaccinated people infected with the delta variant—now the dominant variant in the U.S.—may be contagious and spread the virus to others. Still, Walensky said vaccinated individuals are responsible for a "very small" amount of transmission in the country, with most transmission occurring among unvaccinated individuals.

Because a COVID-19 vaccine is not available for children age 11 and younger and there is a 30% vaccination rate among children ages 12-17, Walensky said the CDC is recommending all individuals regardless of vaccination status wear masks in K-12 schools.

Texas Gov. Greg Abbott has previously prohibited school districts and other governmental entities from imposing a mask mandate. However, several Texas House Democrats sent a letter to Abbott July 23 asking him to reconsider the ban on mask mandates and allow local districts to offer virtual learning.

"As those who represent school districts and parents with grave concerns about returning their children to school under the current conditions, we ask on their behalf that you do the right thing in order to ensure the safety of school communities and the best possible education for Texas children," the letter read.

Walensky continued to urge all Americans to get vaccinated, citing how the vaccine continues to prevent severe illness, hospitalizations and deaths even with the delta variant. The CDC guidance also encourages community leaders promote vaccination and mask wearing in areas with high and substantial transmission.

"With the delta variant, vaccinating more Americans now is more urgent than ever," Walensky said. "The highest spread of cases and severe outcomes is happening in places with low vaccination rates, and among unvaccinated people. This moment, and most importantly the associated illness, suffering, and death, could have been avoided with higher vaccination coverage in this country."

Walensky said masking is a personal choice, but that it is a temporary measure that can help drive down transmission rates. Updating the CDC's mask guidelines was not a decision she or the organization made lightly, Walensky said.

"I know at 18 months through this pandemic, not only are people tired, they're frustrated," Walensky said. "We have mental health challenges in this country; we have a lot of continued sickness and death in this country; our health systems are, in some places, being overrun for what is preventable. And I know, in the context of all of that, it is not a welcomed piece of news that masking is going to be a part of people's lives who have already been vaccinated."