Unlike today's research into gene therapy, which is designed to cure disease, Crakes' vaccine was designed to protect just two people from a pandemic he started . Genetic engineering of humans is also used in Oryx and Crake inappropriately to create the Crakers during Crake's Project Paradice. The Crakers modified their genes to create humans with specific traits. For example, they had skin resistant to ultraviolet rays and the ability to purr to heal themselves. Crake,” has been working on the purr for years. Once it was discovered that the family's cats purred at the same frequency as the ultrasound used on bone fractures and skin lesions and that they had their own self-healing mechanism... the trick was to modify the connected hyoid apparatus and voluntary nerve and control systems of the neocortex have adapted without hindering linguistic abilities” (Atwood