By Martin Baccardax The FDA has approved a second booster shot of Covid vaccines made by Pfizer and Moderna for people over the age of 50. Moderna (MRNA) – Get Moderna, Inc. Report shares jumped higher Tuesday, while Pfizer (PFE) – Get Pfizer Inc. Report extended its recent run of gains, after the U.S. Food & Drug Administration authorized the use of a second shot of Covid boosters developed by the drugmakers. The FDA said adults over the age of 50, as well as those with compromised immune systems, can receiver a booster dose of either the Pfizer or Moderna vaccine at least four months after r…