WATCH: White House defends masking the vaccinated after new CDC guidance

Fox News' Peter Doocy asked White House Press Secretary Jen Psaki about this change. "Why do vaccinated people need to put the masks back on?" Doocy asked.

"It's again, just to go back to this chart," Psaki said, referring to her chart about variants and vaccinations, "Which I will handily point to again, if you are vaccinated it can save your life."

"And I think what this data shows that this pandemic is killing, is hospitalizing, is making people very sick who are not vaccinated. That still continues to be the case regardless of what the mask guidance looks like," Psaki said.

"If vaccines work," Doocy followed-up, "which this sign says that they do, then why do people who have had the vaccine need to wear masks the same as people who have not had it?"

"Because the public health leaders in our administration has made the determination based on data that that is a way to make sure that they are protected, that their loved ones are protected, and that's an extra step, given the transmissibility of the virus that people, that they're advising people."

The CDC announced a reversal in their masking recommendations on Tuesday, instructing even vaccinated Americans to once again wear masks indoors, as the Delta variant continues to make its way through parts of the US.

The agency recommended just two months ago that those who had received two doses of vaccine would no longer require masks in indoor settings. The CDC said as recently as two weeks ago that they had no intentions of changing their guidelines, barring new scientific discovery.

Last week, President Joe Biden said that members of his COVID task force were considering new mask guidelines, due to surges in hospitalizations, mostly of unvaccinated peoples.