Moderna Shares Whipsaw for Third Session After Phase 3 Cancer Vaccine Surge

Moderna shares have swung violently for three consecutive sessions following positive Phase 3 results for its personalized mRNA cancer vaccine, which triggered a roughly 177% single-session rally on August 19. On August 21, the stock plunged 23.55% as heavy profit-taking reversed the prior session's gains, before bouncing 1.31% in pre-market trading and then rallying approximately 8% later in the day alongside a 4% gain in BioNTech, with analysts noting no fresh clinical data had reached the tape to justify continued repricing. JP Morgan responded to the trial readout by more than doubling its price target on Moderna to $77 from $40.

Options activity and implied volatility on the stock ranked among the highest in the market during the period. Separately, disclosure filings revealed that Representative Ro Khanna purchased up to $15,000 of Moderna stock on June 30, 2026, weeks before the trial results became public on August 19.