New research released Friday by the Centers for Disease Control and Prevention reinforces an old message: COVID-19 spreads less in schools where teachers and staff wear masks. Yet the study arrives as states and school districts across the country have begun scaling back or simply dropping their masking requirements for staff and students alike.

With the majority of school-age children still too young to qualify for vaccination, Friday's research is the latest salvo in a simmering fight between public health officials and politicians — with parents lining up on both sides.

The new study comes from Georgia and compares COVID-19 infection rates across 169 K-5 schools. Some schools required teachers, staff and sometimes students to wear masks; some did not.

Between Nov. 16 and Dec. 11, researchers found that infection rates were 37% lower in schools where teachers and staff members were required to wear masks. The difference between schools that did and did not require students to wear masks was not statistically significant.

This is one more study showing that masking, among other mitigation efforts, "can reduce infections and ultimately save lives," said Dr. Sean O'Leary, a professor of pediatrics at the University of Colorado and vice chair of the Committee on Infectious Diseases for the American Academy of Pediatrics.

O'Leary points to a previous CDC study, of schools in Florida, that also found "a strong association with student mask requirements and lower rates of infections in students."

Like any study, Friday's release comes with caveats. Only 12% of schools invited to share their data did so. And it's always worth remembering: Correlation is not causation. Still, the results offer an important warning to states and school districts that are now lifting their school-based mask requirements, especially for adults: It's safer if you don't.

The latest, and perhaps broadest effort to change schools' masking policies comes from Texas, where Republican Gov. Greg Abbott issued an executive order Tuesday banning all mask mandates in the state's public schools. After June 4, the order says, "no student, teacher, parent or other staff member or visitor may be required to wear a face covering."

For Abbott, and many opponents of mask mandates, the move is about restoring a balance between safety and freedom. "We can continue to mitigate COVID-19 while defending Texans' liberty to choose whether or not they mask up," he said in announcing the order.

Zeph Capo, president of the Texas American Federation of Teachers, called the move "unconscionable" in a statement. "The governor's new verdict takes a blanket approach to addressing what is still extremely dangerous for some Texans — a return to school unmasked."

And Texas isn't alone. On Thursday, Iowa's Republican governor, Kim Reynolds, also signed a law banning schools from requiring masks. The justification is similar: "I am proud to be a governor of a state that values personal responsibility and individual liberties," Reynolds said in a statement.

"Whether a child wears a mask in school is a decision that should be left only to a student's parents," South Carolina Gov. Henry McMaster said last week as he issued an executive order allowing parents to opt their children out of school-based mask requirements.

Public health experts have been quick to sound the alarm.

"All along in this pandemic, we have seen the tragic consequences when politics start to play a role in public health decisions. And to me, this kind of maneuver smells like politics — to ban the requirements that are ultimately there to save lives," O'Leary said. "The body of evidence shows us that masks work."

And Dr. Aaron Milstone, a professor of pediatric infectious diseases at Johns Hopkins, likens the banning of mask mandates to having a variable speed limit.

"Unfortunately, with contagious diseases the decisions I make impact someone else," Milstone said. "It would be like saying: You can drive 55 mph if you think that's safe for you, but if someone else thinks they can safely drive 90 mph, their choice may wind up risking your life."

While the CDC recently scaled back its masking guidance for people who are fully vaccinated, the agency also reiterated that schools should continue to require universal masking, at least through the end of the current school year. Though one vaccine has been approved for use for 12- to 15-year-olds, those kids won't be considered fully vaccinated for another month.

Milstone said it's simply too early to talk about schools without masking. "Until vaccines are eligible for all children, it's hard to abandon the practices that we know work the best to prevent the spread of COVID."

Dr. Anthony Fauci, chief medical adviser to the White House, told CNBC this week that it is conceivable the CDC could recommend that middle and high schools be mask-free in the fall — if, that is, enough students 12 years of age and older get vaccinated.

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