A leaked internal CBER memo from FDA official Vinay Prasad laid out proposals to tighten vaccine approvals, urging randomized trials and expanded subgroup data, and prompting immediate market reaction. Public reporting of the memo drove downward pressure on vaccine developers’ shares as investors digested potential new evidentiary burdens. The memo’s publication has elevated scrutiny around how vaccines will be tested and authorized going forward, with stakeholders warning the changes could slow product launches and increase development costs while regulators argue for stronger evidence in vulnerable populations.