Even though 78-year-old James Harrison hates the sight of blood and has a self-professed low pain tolerance, he has been donating blood nearly every week since he was legally old enough. He was inspired to do so after someone else's donated blood saved his life during a chest operation when he was 14.

While all blood donors have the potential to make a difference in someone's life, Harrison is special. The plasma from his blood has the ability to cure a deadly disease.

In Australia, where Harrison lives, rhesus disease—a condition in which a pregnant woman's blood begins attacking her unborn baby's blood cells—was claiming the lives of thousands of babies a year before 1967. If a pregnant woman has rhesus-negative blood and the baby in her womb has rhesus-positive blood, inherited from its father, the mother's body may react by producing antibodies that actively seek out and destroy the baby's "foreign" blood cells, resulting in brain damage or death.

Shortly after his first donation when he was 18, doctors called Harrison with a big announcement: He might be the solution to this mysterious disease, as his plasma contained a rare rhesus antibody. Over the course of the 1960s, Harrison worked with doctors to develop an injection called Anti-D, which prevents expectant mothers from developing the harmful antibodies. Ever since then, Anti-D has been used to successfully ward off rhesus disease throughout Australia.

"Every bag of blood is precious, but James' blood is particularly extraordinary," says Jemma Falkenmire, of the Australian Red Cross Blood Service. "His blood is actually used to make a life-saving medication, given to moms whose blood is at risk of attacking their unborn babies. Every batch of Anti-D that has ever been made in Australia has come from James' blood. And more than 17% of women in Australia are at risk, so James has helped save a lot of lives."

Over 2,000,000, according to estimates by the Australian Red Cross blood service.

Since the discovery, Harrison has donated plasma more than 1,000 times. But his opportunities are dwindling. In Australia, people must retire from plasma donation at the age of 81, which is just three years away for Harrison.

"I guess for us the hope is there will be people who will donate, who will also ... have this antibody and become life savers in the same way he has, and all we can do is hope there will be people out there generous enough to do it, and selflessly in the way he's done," says Falkenmire.

[h/t CNN]