Moderna stock rose 9%. Pfizer shares rose 1.6% in afterhours trade and its partner BioNTech, which developed the vaccine, rose 4.2%.Both vaccine candidates rely on a new technology that allows for faster development and manufacturing than traditional vaccine production methods but does not have an extensive track record.So-called mRNA, or synthetic messenger RNA (mRNA), teaches the immune system to recognize and neutralize the coronavirus by mimicking its surface.Moderna, which has never brought a vaccine to market, has received nearly $1 billion from the U.S.