President Biden was never shy of criticizing former President Trump for his messaging on coronavirus, but just over a week into his presidency his administration is already walking back statements he has made about the pandemic and vaccine rollout.

On Monday, Biden was optimistic, saying that by springtime anyone who wants to get a vaccination would be able to do so.

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"I think it will be this spring. I think we’ll be able to do that this spring. But it’s going to be a logistical challenge that exceeds anything we’ve ever tried in this country," the president said. "But I think we can do that."

And looking forward, he added, "I feel confident by summer we’ll be well on our way towards herd immunity and increasing the access."

The next day, White House press secretary Jen Psaki took back that message.

"What the president’s goal is, is ensuring that there’s greater availability in the spring," Psaki said. "But the fact is," she added, "every American is not going to be eligible this spring."

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This flip-flop on vaccine availability came after Biden's new head of the Centers for Disease Control and Prevention admitted that the president's goal of vaccinating 100 million people in 100 days was not enough for the U.S. to contain the pandemic in 2021.

"Yes, we have to go faster," CDC's Dr. Rochelle Walensky told "Fox News Sunday," acknowledging that the administration is "limited by numerous constraints," particularly supply.

Biden's nominee for Surgeon General, Dr. Vivek Murthy, echoed the sentiment that the administration's vaccination goal is on the low side.

"That’s a floor, that’s not a ceiling," Murthy told "This Week" host George Stephanopoulos on ABC. "We've got to increase supply, which we can do using the Defense Production Act, but we have to set up distribution channels like mobile units that can reach people."

On Friday, Biden caused a stir with a pessimistic message when he stated, "There’s nothing we can do to change the trajectory of the pandemic in the next several months."

That statement too was walked back soon after, when Biden's nominee for Secretary of Health and Human Services Xavier Becerra tried to clarify the president's message.

"I believe President Biden made it very clear, the plane is in a nosedive, and we gotta pull it up. And you’re not going to do that overnight," Becerra told "State of the Union" host Dana Bash on CNN. "But we're gonna pull it up, we have to pull it up. Failure's not an option here, and so we will."

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When asked if that means he believes the administration can indeed change the pandemic's trajectory, Becerra reiterated that it would not happen "overnight," but said that progress is possible if people work together.

"We've got to make sure we're coordinated," he said. "We can't just tell the states, 'Here's some PPE, some masks, here's some vaccines, now go do it.' No, no. When we hand them over, we stay with them and provide resources to make it happen."

Fox News' Brooke Singman and Peter Aitken contributed to this report.