Dr. Rochelle Walensky says there are several reasons why she recommended COVID-19 booster shots for older Americans and frontline workers.

“These are people among the people who are vaccinated first, they are sort of longer into their vaccine than many of the other Americans are.” Walensky told “NewsNation’s” Joe Donlon on “The Donlon Report” on Monday.

“The second reason is because (frontline workers) are every day on the frontlines confronting people, oftentimes with COVID, who they are taking care of, they are caring for the most vulnerable, they’re often taking care of or teaching the unvaccinated in our young in our schools.” 

US Health Officials ruled late Thursday on who’s eligible for the booster shot: Americans 65 and older and others vulnerable because of underlying health problems or where they work and live — once they’re six months past their last dose.

Walenksy said the booster campaign is one of the many steps that the White House is focusing on. 

“This is a really important first step to our booster program, but certainly not our last,” she said. “We have many more steps to go and we will be following the data in real-time and updating these guidances.”

Earlier today, President Biden received his booster shot at the White House. “Boosters are important,” Biden said. “But the most important thing we need to do is get more people vaccinated.”

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

There have been some concerns about the efficacy of COVID-19 vaccines after a number of recent studies indicated a growing number of “breakthrough” cases among the fully vaccinated.

However, Walensky said the vaccines still offer strong protection against serious illness for all ages.

“In fact, we know that people who are unvaccinated still have 10 times the risk of being admitted to the hospital and 11 times the risk of dying … compared to people who are vaccinated even today,” she said.

For now, Walensky said only people who got the Pfizer primary series are eligible for the booster shot, but she said the CDC is looking into the Moderna and Johnson & Johnson vaccines. 

“We anticipate that you, too, will need a boost. We are awaiting … the submission of packages from the manufacturing to the FDA, and as soon as the FDA has those packages, they will address them with urgency, and we (at the CDC) will do the same. 

She said she anticipates those recommendations will come in the next few weeks.