By Michael Erman

(Reuters) – U.S. regulators are expected to authorize a third booster shot of the Pfizer (NYSE:) Inc/BioNTech SE COVID-19 vaccine for older and some high-risk Americans early this week in time for the government to roll them out by Friday as hoped.

In the days leading up to Wednesday’s meeting of advisors at the U.S. Centers for Disease Control and Prevention, the Food and Drug Administration will likely give their approval to shots for this or another group. More specific recommendations will be made by the CDC panel regarding how shots should be administered.

An FDA advisory committee recommended emergency authorization of additional Pfizer shot for Americans aged 65 or older, and individuals at highest risk of developing severe illnesses.

The FDA advisory committee had previously voted against broadening approval. They said there wasn’t enough evidence for widespread use and they needed more safety data especially regarding the risks of developing heart disease in young people following vaccination.

While the FDA may not follow this panel’s recommendations, they usually do.

In the future, the agency may revisit booster shots in order to obtain a larger authorization. The FDA’s top members are divided on whether booster shots are necessary. Janet Woodcock, interim head of FDA, supports them while some scientists at the agency argue they don’t need to be used yet.

Although the authorization proposal is limited, it would still apply to most Americans who were vaccinated in the early phases of the U.S. vaccine campaign. This could be because their immunity might be declining.

Norman Baylor, chief executive of Biologics Consulting and former director of FDA’s Office of Vaccines Research and Review, said the decision gives FDA additional time to understand what data is required to approve booster shots broadly.

Baylor acknowledged that the decision gives FDA some breathing room.

Baylor said that while health officials indicated they believe boosters will eventually be recommended for large swathes of the population they advised Americans to not seek out booster doses until the FDA has given their approval.

President Joe Biden’s chief medical adviser, Dr. Anthony Fauci, told CNN on Sunday that the data needed to determine the advisability of booster shots of the Moderna (NASDAQ:) Inc and Johnson & Johnson (NYSE:) COVID-19 vaccines is just weeks away.

Some countries including Israel have begun COVID-19 boost campaigns, as has Britain. According to the CDC, 2 million Americans had received a third shot and were eligible for additional shots from the United States.