Katharine Gammon 06.19.12 2:05 AM Keeping vaccines cold enough for them to survive is one of the largest challenges of global health efforts. A new breakthrough uses silk to dramatically increase the temperature at which a vaccine can live—which could save millions. Newsletter Get the latest Fast Company stories delivered to your inbox daily. Send I'd also like to receive special Fast Company offers ARE YOU REGISTERED TO VOTE? Register now to make sure you have a voice in the election.