Companies warned that proposals under the Trump administration and statements by Health Secretary Robert F. Kennedy Jr. could force major changes to vaccine formulations and schedules. Reporting and investigative coverage revealed administration officials exploring restrictions on vaccine adjuvants and combined formulations—moves that vaccine manufacturers say would require years and large investments to redevelop affected products and could disrupt childhood immunization coverage. Industry groups and public‑health experts cautioned that rapid policy changes could reduce vaccine availability and raise public‑health risks. The debate has already prompted intense conversations between manufacturers, regulators and lawmakers about supply chain resilience, regulatory pathways and the downstream clinical implications of reformulating long‑standing vaccines.