"I would wish that the federal government could speak with one voice," said UCSF's Dr. George Rutherford.
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A review published in a top medical journal "The Lancet" argues there isn't strong enough data to warrant booster shots are needed for the general population already vaccinated, citing the vaccine's efficacy is still high enough to prevent severe disease and death. The report has 18 co-authors, including two high-ranking FDA officials that resigned over the controversy.
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"This is one of these questions about the perfect is the enemy of the good," said Rutherford. "These guys want perfection. You'll probably have to make a decision on less than perfect data."
Rutherford says he's concerned the mixed messaging will result in added confusion and vaccine hesitancy.
"Clearly it will make dissonance for people," he said. "The timing and whether you should get it or not."
WATCH: COVID booster shots: Who will get them? When? And why?
What do we know about booster shots for COVID-19?
Most of the authors in the published review are from overseas, including experts from the WHO that are calling for a COVID booster moratorium until 2022. Stanford Infectious Disease Dr. Jorge Salinas supports that move.
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"While at a personal level there may be a slight benefit of a third dose," said Salinas. "There is a tremendous benefit if that dose goes to somebody else that has not been vaccinated."
The FDA's advisory committee will meet this Friday to review Pfizer COVID booster shot data before the CDC makes a final decision on approval.