COVID-19 vaccine maker Moderna, Inc. MRNA fell over 21% on Thursday after the company reduced its revenue guidance for the year, citing a highly competitive respiratory vaccine market in the U.S. and weak COVID-19 vaccine sales in Europe. What Happened: Moderna stock plunged 21.01% to $94.17 on Thursday and fell an incremental 1.73% to $92.54 in premarket trading on Friday, according to Benzinga Pro data. Cathie Wood's Ark Invest capitalized on the weakness and piled into the stock. On Thursday two of Ark's ...