(NewsNation Now) — President Joe Biden received a COVID-19 booster shot Monday afternoon, days after the Centers for Disease Control and Prevention endorsed the additional dose of the Pfizer vaccine for all Americans 65 and older.

“Boosters are important,” Biden said. “But the most important thing we need to do is get more people vaccinated.”

Biden, 78, got his first shot on Dec. 21 and his second dose three weeks later, on Jan. 11, along with his wife, Jill Biden. It was not immediately clear whether the first lady, who’s 70, would also receive the booster dose on Monday.

At least 2.66 million Americans have received booster doses of the Pfizer vaccine since mid-August, according to the CDC. 

U.S. health officials late Thursday endorsed the additional Pfizer jab for older Americans — along with tens of millions of younger people who are at higher risk from the coronavirus because of health conditions or their jobs.

Biden last week urged those now eligible for COVID-19 booster shots to get the added protection and praised the decision and aimed to set aside any unease about the vaccination.

“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?”

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

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.