Twelve former FDA commissioners publicly criticized CBER Director Vinay Prasad's plan to tighten vaccine update requirements in a New England Journal of Medicine piece, arguing the proposal risks undermining established vaccine policy. The rebuke was filed after a leaked Prasad memo described longer, larger studies before manufacturers can update vaccines. Prasad defended his approach at a closed investor conference, calling media narratives “misleading” and framing the changes as modernization. Sources told STAT that Prasad emphasized risk-based, larger trials to support vaccine strain changes. The exchange spotlights a rare, public split between career regulators and ex-commissioners and signals heightened political and scientific scrutiny inside FDA leadership. CBER (Center for Biologics Evaluation and Research) oversees biologics and vaccines; changes there would reshape how manufacturers submit evidence for routine vaccine updates, affecting timelines for seasonal and pandemic responses.