Five‑year follow‑up data show adding Merck and Moderna’s investigational cancer vaccine to Keytruda sustained a 49% reduction in risk of recurrence or death in melanoma, reinforcing the combination’s long‑term benefit signal. The follow‑up bolsters the companies’ phase 3 strategy and supports ongoing development of mRNA vaccine platforms paired with PD‑1 blockade. The result extends earlier efficacy signals and will factor into regulatory and commercialization planning if phase 3 confirms benefit. Investors and peers are watching whether the durability observed in melanoma translates to other tumor types where vaccines are under study.