Moderna pulls back after massive gains on cancer vaccine trial results

Merck & Co

20/08/2026 15:57

Updates

        ** Shares of Moderna MRNA.O tumble 20.5% to $139.30, while Merck MRK.N falls 1.9% at $149.35
** Pullback follows a blistering rally a day earlier that more than doubled Moderna's stock, adding more than $44 billion in market value
** The companies said on Wednesday a personalized mRNA cancer vaccine together with Merck's immunotherapy Keytruda reduced the risk of recurrence and spread of melanoma in a late-stage trial
** MRNA set for biggest one-day percentage drop in more than two years, if losses hold. The slump is on track to erase about $14.3 billion in market value at the current level
** "While we were thrilled to see a positive market reaction for the definitive success of the therapeutic cancer vaccine, intismeran autogene, the reception was overly optimistic and creates expectations that we believe will be difficult to meet," Leerink Partners analysts say 
** MRNA shares are still up more than 500% from their 52-week low of $22.28 hit in November 2025
** Including session's move, MRNA's stock has gained 368%, MRK is up 42% YTD 

 (Reporting by Akriti Shah, Mariam Sunny and Kamal Choudhury in Bengaluru)
 ((akriti.shah@thomsonreuters.com ; X, formerly Twitter: @AkritiShahh))