A vaccine that can teach the immune system to attack any type of cancer is being developed and tested by scientists in Germany. Cancer affects one person in every three. It's caused by genetic damage to our cells, which leads them to grow in an uncontrolled and invasive way. But because the cancer cells are part of our own body, the immune system normally ignores them because they're regarded as non-hostile. What Ugur Sahin and his colleagues are doing is to identify a series of chemical markers that are unique to a patient's cancer cells and then turn these into a genetic message that is injected into the bloodstream. Because it's packaged up to resemble an infection, it re-programmes the immune system's white blood cells - or lymphocytes - to track down the tumour and destroy it. Chris Smith learnt all about it...