Moderna and Merck shares slump as melanoma vaccine data fail to impress market

Moderna and Merck shares fall as the two companies' highly anticipated personalized melanoma vaccine data failed to convince investors that a new era in cancer treatment has arrived. The companies announced in August that the customized vaccine, when used in combination with Merck's blockbuster drug Keytruda, could significantly reduce the risk of recurrence of this deadly tumor, with clinical significance. The full trial data leaked on Thursday fell short of the high expectations Wall Street had formed earlier this year. Although the trial results clearly showed the vaccine is effective, they were not impressive enough to convince the market that Moderna and Merck can achieve the broader goal of pioneering a new approach to treating multiple cancers. Moderna shares plunged 18%, while Merck fell 1.8%.