Moderna Shares Fall 25% After Melanoma Vaccine Phase 3 Data

Moderna shares fell 25.2% to $183.88 on October 22, 2026, the stock's steepest one-day percentage fall, per Reuters, erasing about $24 billion in market value. The drop followed Merck and Moderna's Phase 3 melanoma vaccine data. Topline success was announced August 19; full results are slated for ESMO 2026.