National Nurses United, the nation’s largest union of registered nurses, is lauding CDC director Rochelle Walensky’s inclusion of front-line and health care workers in her recommendations for who may now get a third Pfizer booster dose -- a decision which overruled the agency’s independent panel conclusion.

The CDC’s advisory group had rejected the idea of third Pfizer doses for “high risk” workers like nurses and teachers, saying that without further data it wasn’t comfortable with automatically adding younger, healthier people simply by occupation.

The nurses' union urged Walensky to bypass what her advisory panel had said -- which is what she ultimately did.

“Nurses across the country are beyond relieved today to wake up to the news that CDC Director Rochelle Walensky prioritized the health and safety of health care and other essential workers most at risk of contracting Covid-19,” NNU president Deborah Burger told ABC in a statement Friday.

“It takes courage to do the right thing, especially when it involves going against the CDC’s own advisory panel," Burger added. "We applaud this bold decision-making that prioritizes the health and safety of workers on the front lines of this ongoing crisis, and we know that her decision will absolutely save lives.”

Walensky however, insisted that she did not overrule the CDC’s advisory panel’s decision on booster shots for at-risk, front-line workers. She defended the decision as a “scientific close call” saying that she would advocate for the boosters if she was in the room.

"I want to be very clear that I did not overrule … the advisory committee," she said. “I listened to the votes. I listened to the comments on the vote and this was a scientific close call ... It was my call to make. If I had been in the room, I would have voted 'yes.'"

She also said that boosters were not a solution for ending the pandemic.

"I want to be clear we will not boost our way out of this pandemic. Infections among the unvaccinated continue to fuel this pandemic rise, resulting in a rising number of cases, hospitalizations and deaths where people are in vaccinated," Walensky said.

-ABC News' Sasha Pezenik and Matthew Vann

On the heels of pharmacy retail chain Walgreens' announcement that it is now ready to give third booster doses of the Pfizer vaccine to newly eligible groups, CVS announced it too will be ready "later today."

"We are reviewing the CDC guidance and will be ready to provide the booster dose at CVS Pharmacy and select MinuteClinic locations that offer the Pfizer/BioNTech vaccine later today. We strongly encourage customers to schedule an appointment in advance at to ensure they are able to access the correct vaccine at a convenient time and location," the drugstore chain said in a statement Friday.

-ABC News' Sasha Pezenik

School districts without a universal masking policy in place at the start of the school year saw a significant increase in COVID-19 outbreaks, according to three new studies released by the Centers for Disease Control and Prevention.

Additionally, school districts in those counties saw more than double the number of pediatric COVID-19 cases during this same period, the studies, released Friday, also found.

The studies further emphasize that school mask requirements, along with other prevention strategies, are critical to reducing the spread of COVID-19 in schools.

Other key findings from the studies include:

- Schools in Arizona that opened without a school mask requirement had a 3.5 higher likelihood of having a COVID-19 outbreak than schools that opened with a school mask requirement.

-During the early part of the 2021-2022 academic school year, almost 2,000 schools have been closed and more than 900,000 students in more than 40 states have been impacted.

- Pediatric cases during the start of the 2021-2022 school year were about half in U.S. counties with school mask requirements than in counties without school mask requirements.

To prevent COVID-19 outbreaks in schools, the CDC recommends a multi-layered strategy including vaccination, universal indoor masking, testing and physical distancing.

-ABC News' Eric Strauss

Walgreens announced Friday morning that its participating stores are ready to start giving third booster doses of Pfizer's vaccine to newly eligible groups.

The CDC greenlit Pfizer booster shots on Thursday.

As of Friday morning, those newly eligible groups can walk into any Walgreens location offering the Pfizer shot, the company said.

Also, as of Saturday, people can begin scheduling appointments online or over the phone.

-ABC News' Sasha Pezenik