A leaked internal memo from CBER director Vinay Prasad proposing major changes to vaccine approval and use prompted market and policy ripples. The document questions pandemic‑era shortcuts and calls for randomized trial evidence for many products and populations; the revelation coincided with a drop in vaccine developers’ stocks. BioCentury reported that Prasad’s memo frames a shift toward stricter evidentiary standards and implementation changes at the FDA and ACIP. Market reaction reflected investor concern about longer, costlier development pathways for vaccines and modified shots. Companies and policy observers are parsing the proposals for implications on timelines, pediatric approvals and annual vaccine programs; regulators have signaled further public deliberations before any formal rulemaking.