Call it hollow-hearted. Researchers have built a mimic of the outer capsule of the foot-and-mouth disease virus. Inside, where the virus' genetic material normally lives, is empty. Such synthetic virus-like particles could go into a foot-and-mouth vaccine that's cheaper to make because it doesn't require the tight biosecurity that a factory that makes vaccines from live viruses needs, its creators say. The researchers have also built the virus mimic in such a way that it can stay out of a refrigerator for longer than current foot-and-mouth vaccines, so it could ship more easily around the world.