Moderna Slides Up to 25% as Cancer Vaccine Meets Sky-High Expectations

Moderna shares fell as much as 25% on Thursday despite positive data for intismeran autogene, a personalized shot aimed at mutations in an individual’s tumor. In a melanoma trial, the vaccine, paired with Merck’s immunotherapy Keytruda, reduced recurrence or death risk by 42% in certain patients; about 82% were alive without recurrence at two years versus 70% on Keytruda alone, and the combination cut distant spread or death risk by 38%. The trial covered only melanoma, and full phase 3 results are due at the European Society for Medical Oncology conference this weekend. Moderna stock was still up more than 530% for 2026 as of Thursday afternoon.