James Harrison's blood contains an antibody that is made into a vaccine that has saved countless children.

James Harrison had one of his lungs removed at the age of 14. His operation was a success even though James had lost a lot of blood. When he learned he was alive thanks to unknown blood donors around Australia, James set out to donate blood himself.

James had to wait until he was 18 to be legally allowed to start donating. Soon, doctors noticed something special about James' blood. There was a very rare antibody—possibly the result of the numerous transfusions—flowing through James that had the potential to save the lives of unborn children.

Rhesus disease is a condition that occurs in pregnancy in which the mother's blood cells attack the blood cells of the fetus. The child's blood cells are treated like foreign bodies and infection by the mother's body. The worst cases of rhesus disease result in death or brain damage for the unborn child. The antibody in James' blood was turned into a vaccine called Anti-D that prevents the production of the attacking antibodies. In Australia, it's estimated that 17% of women are at risk for rhesus disease.

Sources: CNN