After days of extensive debates among vaccine experts, the U.S. Centers for Disease Control and Prevention (CDC) officially confirms that booster shots of the Pfizer/BioNTech Covid-19 vaccine can be administered to some of the nation's adults.

Early Friday morning, CDC Director Dr. Rochelle Walensky recommended boosters for people ages 18 to 64 who are at increased risk of COVID-19 due to their workplaces or institutional settings, in addition to older adults, long-term care facility residents and some people with underlying health conditions.

This decision was out of harmony with the advice given Thursday by the CDC's independent Advisory Committee on Immunization Practices.

The committee on Thursday voted to recommend boosters for people age 65 and older and residents of long-term care facilities who received the Pfizer/BioNTech COVID-19 vaccine series at least 6 months ago, and people ages 50 to 64 with underlying medical conditions.

But, ACIP members voted 9-6 against recommending boosters for people ages 18 to 64 who were at greater risk because of their occupational or institutional settings, such as health care workers, caregivers for the seriously ill, individuals in homeless shelters and in correctional facilities.

Instead of following the ACIP's vote, Director Walensky's recommendation reflected the stance of the US Food and Drug Administration (FDA) which, on Wednesday, provided emergency use authorization for a booster dose of Pfizer's COVID-19 vaccine in people 65 and older, people at high risk of severe disease and people whose jobs put them at risk of infection.

"As CDC Director, it is my job to recognize where our actions can have the greatest impact," Walensky said in the statement. "I believe we can best serve the nation's public health needs by providing booster doses for the elderly, those in long-term care facilities, people with underlying medical conditions, and for adults at high risk of disease from occupational and institutional exposures to COVID-19."

She continued, "This aligns with the FDA's booster authorization and makes these groups eligible for a booster shot. Today, ACIP only reviewed data for the Pfizer-BioNTech vaccine. We will address, with the same sense of urgency, recommendations for the Moderna and J&J vaccines as soon as those data are available."

Pfizer asked the FDA for full approval of a booster dose for people 16 and older six months after they were fully immunized with two shots. The company said it had enough evidence that immunity starts to wane after six months and that giving a booster restores the immunity safely.

More data on booster doses is being generated in the United States and Israel and increased eligibility for boosters may become an option in the future.

Moderna has also asked the FDA to authorize booster shots for its vaccine, but so far the FDA has only considered Pfizer's bid.

Johnson & Johnson released data this week that it said showed a booster dose greatly raised immunity, but the company has yet to apply with the FDA to consider a booster vaccine dose.