While Pfizer and Moderna are pushing for COVID-19 vaccine booster shots, staff at the Food and Drug Administration (FDA) are yet to take a stance, citing a lack of verified data. In a 23-page document (pdf) published to the agency’s website on Wednesday, FDA staff noted that the expected benefits of booster vaccinations depend entirely on the impact they have on “reducing disease relative to the primary series.” The documents serve as a brief for the FDA’s Vaccines and Related Biological Products Advisory Committee, which is meeting on Sept. 17 to review Pfizer’s request to apply for a third “booster” dose of the vaccine in individuals aged 16 years and older. “If the primary series of COMIRNATY [Pfizer Comirnaty vaccine] is still effective in preventing important COVID-19-related outcomes, then the benefit of booster vaccination is likely to be more limited than if effectiveness following the primary series has waned substantially,” FDA staff wrote. “Factors supporting licensure of a booster dose …