RE:RE:RE:RE:Wolf in sheep's clothing But the Motley Fool Why Moderna Stock Dropped Today The biotech's coronavirus vaccine reportedly made some people sick. Joe Tenebruso(TMFGuardian) May 27, 2020 at 4:47PM What happened Shares of Moderna (NASDAQ:MRNA) plunged on Wednesday, following reports that several of the participants in its novel coronavirus vaccine trial suffered an adverse reaction to its experimental drug mRNA-1273. By the close of trading, Moderna's stock was down 9.5% after falling as much as 20% earlier in the day. So what Moderna's stock surged 20% on May 18 after it shared positive results from its phase 1 study for its COVID-19 vaccine candidate mRNA-1273. That same day, the biotech announced a stock sale and raised more than $1.2 billion in cash, which it said it would use to manufacture its coronavirus vaccine should it prove safe and effective.