For years, Bill and Melinda Gates have been warning about the threat of a global pandemic. Now they are fighting as hard as they can to save lives as the world struggles to combat Covid-19. The Gates Foundation is making billions of dollars available, in part to develop eight different vaccines, hoping to find one that works. In an exclusive interview, Melinda warns of the impact the coronavirus has on the most vulnerable communities in the United States and the risk it poses in the developing world.