US Stock of the Day | Kabutaro & Friends

On August 21, 2026, the most talked-about US stock online is Moderna<MRNA>.
Background: On August 19, Moderna announced that its personalized mRNA cancer vaccine Intismeran (mRNA-4157), developed with Merck, showed reduced melanoma recurrence risk in a Phase 3 trial, sending shares up a record 177% that day, from $62.96 to $174.38, the stock's largest single-day gain ever. The surge inflicted roughly $5.5 billion in paper losses on short sellers. The following day, August 20, shares reversed sharply, falling as much as 23.9% intraday to $132.70, and most recently traded around $146.21, down 16.2% from the prior day's high of $174.38 but up 7.2% from its low of $136.35. Trading volume reached 47.73 million shares, well above the average of 25.22 million. Bank of America upgraded its rating from Underperform to Neutral and raised its price target from $40 to $170.