Covid vaccine makers' stocks soar on Omicron variant concerns last week. Moderna Stock Slides After CEO Says Current Vaccines Will Struggle Against Omicron. Shares of Covid-19 vaccine makers jumped on Friday, and again early on Monday, as global health officials sounded alarms about the new variant known as Omicron first identified in southern Africa. As Omicron Wreaks Havoc on the Market, How Should Vaccine Makers Respond? $Pfizer(PFE)$ $Pfizer(PFE)$ closed out November trading with its best monthly advance in 30 years, as renewed virus fears revive the market’s focus on vaccine makers. The stock rose 2.5% to $53.73 in New York trading on Tuesday, ending the mo