Vaccines protect you from nasty diseases like polio by priming your body's immune system to fight off invading disease organisms. Most of these have to be injected into you with a needle and syringe and it hurts a bit. I guess you, like most kids, don't like having vaccinations much. So imagine if you could get your vaccination by eating a potato or a banana! This is one of the good things GE could do but it could also be very dangerous if not carefully monitored. The production of pharmaceuticals like vaccines by making genetically engineered plants or animals is called Pharming.