ATLANTA (NewsNation Now) — President Joe Biden on Friday urged those now eligible for COVID-19 booster shots to get the added protection a day after the Centers for Disease Control and Prevention endorsed the doses for millions of older or otherwise vulnerable Americans.

Opening a major new phase in the U.S vaccination drive against COVID-19, CDC Director Dr. Rochelle Walensky signed off on a series of recommendations from a panel of advisers late Thursday. Biden praised the decision and aimed to set aside any unease about the vaccination, saying that he would get his own booster soon.

“It’s hard to acknowledge I’m over 65, but I’ll be getting my booster shot,” Biden said. “It’s a bear, isn’t it?”

The advisers said boosters should be offered to people 65 and older, nursing home residents and those ages 50 to 64 who have risky underlying health problems. The extra dose would be given once they are at least six months past their last Pfizer shot.

However, Walensky decided to make one recommendation that the panel had rejected.

The panel voted Thursday against saying that people can get a booster if they are ages 18 to 64 years and are health care workers or have another job that puts them at increased risk of being exposed to the virus.

But Walensky disagreed and put that recommendation back in, noting that such a move aligns with a Food and Drug Administration booster authorization decision earlier this week.

An administration official said the White House did not have input in Walensky’s decision nor was given a heads-up. Biden on Friday said “the decision is left to the scientists and the doctors. That’s what happened here.”

“As CDC Director, it is my job to recognize where our actions can have the greatest impact,” Walensky said in a statement late Thursday night. “At CDC, we are tasked with analyzing complex, often imperfect data to make concrete recommendations that optimize health. In a pandemic, even with uncertainty, we must take actions that we anticipate will do the greatest good.”

Walensky’s change was unusual. Traditionally, CDC directors accept the advisory committee’s recommendations without making substantive changes.

Experts say getting the unvaccinated their first shots remains the top priority, and the panel wrestled with whether the booster debate was distracting from that goal. Biden stressed that the administration’s focus remained on getting people to get their first shots and that he intended to keep rolling out “vaccination requirements wherever I can.”

“The refusal to get vaccinated have cost all of us,” the president said. “It is not hyperbole: it is literally a tragedy. Don’t let it be your tragedy.”

All three of the COVID-19 vaccines used in the U.S. are still highly protective against severe illness, hospitalization and death, even amid the spread of the extra-contagious delta variant. But only about 182 million Americans are fully vaccinated, or just 55% of the population.

“We can give boosters to people, but that’s not really the answer to this pandemic,” said Dr. Helen Keipp Talbot of Vanderbilt University. “Hospitals are full because people are not vaccinated. We are declining care to people who deserve care because we are full of unvaccinated COVID-positive patients.”

About 26 million Americans got their last Pfizer dose at least six months ago, about half of whom are 65 or older. It’s not clear how many more would meet the CDC panel’s booster qualifications.

CDC data shows the vaccines still offer strong protection against serious illness for all ages, but there is a slight drop among the oldest adults. And immunity against milder infection appears to be waning months after people’s initial immunization.

Among people who stand to benefit from a booster, there are few risks, the CDC concluded. Serious side effects from the first two Pfizer doses are exceedingly rare, including heart inflammation that sometimes occurs in younger men. Data from Israel, which has given nearly 3 million people — mostly 60 and older — a third Pfizer dose, has uncovered no red flags.

The U.S. has already authorized third doses of the Pfizer and Moderna vaccines for certain people with weakened immune systems, such as cancer patients and transplant recipients. Other Americans, healthy or not, have managed to get boosters, in some cases simply by asking.

The Associated Press contributed to this report.