Merck Stock Hits Record High After Cancer Vaccine Breakthrough

Merck & Co.'s stock price has been fluctuating in the high $140s in August 2026, just below its reported all-time high of $153.53.

This comes after strong Phase 3 melanoma cancer vaccine data with a partner sparked a sharp rally and pushed the shares into record territory as of August 20, 2026.

The personalized mRNA cancer vaccine for melanoma, used together with Merck's immunotherapy drug Keytruda, achieved its primary endpoint in a large Phase 3 trial, contributing to a broad move higher in both the vaccine partner and Merck on August 20, 2026.

Merck's shares opened at $152.21 that day, reflecting a 12.6% gain versus a prior reference level and underscoring how the vaccine news has reset expectations for the company's oncology franchise.