Moderna (NASDAQ:MRNA) stock is on the rise Friday as the company prepares to join the S&P 500. Source: Shutterstock MRNA stock is set to join the S&P 500 before trading starts on Wednesday. The reason for Moderna joining has to do with a deal between Alexion Pharmaceuticals (NASDAQ:ALXN) and AstraZeneca (NASDAQ:AZN). This will have AstraZeneca…