Reporting shows the Trump administration, guided by Health Secretary Robert F. Kennedy Jr., is considering policy changes that could restrict adjuvant use and reformulate multi‑disease combination vaccines on the U.S. childhood schedule. Vaccine manufacturers have privately warned these proposals could force them to redevelop key vaccines, a process that could take years and cost up to a billion dollars per product. Industry sources say sudden ingredient or formulation mandates risk immediate supply disruptions and could weaken protection against diseases like measles, mumps, and polio. Public‑health officials and manufacturers are assessing timelines, technical feasibility, and the regulatory pathway for any rapid reformulation. The debate raises questions about regulatory predictability, manufacturing capacity, and the downstream effects on vaccination coverage and global supply chains.