WATCH: Fox News’ Peter Doocy grills Psaki over Biden suggesting Republican states were ‘Neanderthals’. CDC has since confirmed that red states were correct

Doocy starts, "There are a lot of questions about the timing of the CDC's announcement yesterday, So, did somebody at the Biden administration or in the Biden administration update these guidelines for political reasons?"

"No," answered Psaki.

"So was the medical or scientific reason? What was the 'big breakthrough', to do this yesterday?"

"Well, I know that Dr. Walensky did an extensive amount of interviews yesterday to answer that," responded Psaki, stating that "her entire team of health and medical experts are constantly reviewing the data to ensure that they can provide accurate updates and guidance to the American people."

Psaki then mentioned that "vaccines work in the real world", "vaccines stand up to the variants", and "vaccinated people are less likely to transmit the virus."

Doocy then continued, "Looking at the CDC's website on the way up here, only 45.6 percent of US adults have been fully vaccinated as of yesterday. Only 58.9 percent of the the adult population has had at least one dose."

"So, what happened to President Biden saying in March saying that he thought lifting mask mandates before every adult American goes and gets a shot is 'Neanderthal thinking'?"

"Well, first let me say that the president, our North Star [sic], has been listening to the guidance of our health and medical experts and teams, and that's exactly what we're doing in this case."

"And just to reiterate, the CDC, the doctors and medical experts there, were the ones who determined what this guidance would be, based on their own data, and what the timeline would be."

"That was not a decision directed by, made by the White House; the White House was informed of that decision."