Moderna Shares Drop 25% After Skin Cancer Vaccine Trial

Moderna shares fell 25.2% to $183.88 on October 22, 2026, their steepest one-day percentage drop, per Reuters, wiping out about $24 billion in value. The drop followed late-stage trial results for a Merck and Moderna vaccine against melanoma, a serious skin cancer. Main results were positive, announced August 19; full details come at ESMO 2026, a major cancer conference.