“Having just one vaccine is not going to cut it. We’re probably going to need two or three different vaccines in order to vaccinate the billions of people around the world that are going to need to be vaccinated,” Dr. Carlos del Rio, executive associate dean at the Emory School of Medicine and Grady Health System and co-investigator for Moderna’s coronavirus vaccine trials, told CNBC’s “Squawk Box” Tuesday. “The issue is going to be if one is 90% and the other is 70%, what are we going to do?”