James Harrison, 78, of Australia, is "The Man With the Golden Arm."

For over 60 years, Harrison has been a blood donor, since a life-saving transfusion he himself received at the age of 14.

The vow a grateful Harrison made at the time to give back has paid off more than two million times over.

Harrison's blood carries extremely rare antibodies which are the key to stopping the deadly Rhesus disease in its tracks.

Rhesus disease occurs when a pregnant woman with Rhesus-negative (RhD-negative) blood is carrying a baby with Rhesus-positive (RhD-positive) blood from its father. Her blood cells, perceiving the baby's as foreign, attack the baby's, often resulting in brain damage or even death by miscarriage for the fetus.

The antibodies in Harrison's blood are the key ingredient in "Anti-D," a vaccine which enables RhD-negative mothers to carry RhD-positive babies safely to full-term and give birth to healthy children.

One of Harrison's biggest fans is Kristy Pastor, who just gave birth to Samuel, her fourth healthy baby, thanks to Harrison's weekly blood donations:

They just said you needed the vaccine. I didn’t think about it any further, and then looking into it a bit more, I found out about James and how amazing he is and how many donations he’s made, and that it was all because of him. I’m grateful and I think James is really selfless to continue to donate, so that we can keep having this vaccine.

No one knows for sure how Harrison developed his rare blood antibodies, but those in the know believe there must be others. Says Jemma Falkenmire, of the Australian Red Cross Blood Service:

I don’t think anyone will be able to do what he’s done, but certainly we do need people to step into his shoes. He will have to retire in the next couple years, and 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.

For his part, there's only one thing Harrison refuses to do:

Never once have I watched the needle go in my arm. I look at the ceiling or the nurses, maybe talk to them a bit, but never once have I watched the needle go in my arm. I can’t stand the sight of blood, and I can’t stand pain.

And yet, he continues saving lives.