James Harrison is 78 and has donated blood nearly every week for the last 60 years.

Known as “The Man with the Golden Arm,” the Australian discovered his blood was extremely valuable when he first went to donate at the age of 18.

Doctors noticed his blood contained a rare antibody which held the solution to a deadly condition called Rhesus disease. In Australia at the time, thousands of babies were dying in utero and at birth due to the condition which causes a pregnant woman’s blood to actually start attacking her unborn baby’s blood cells.

Pic via CNN

If a woman has rhesus-negative blood and her baby has rhesus-positive blood, the mother's body can develop antibodies that begin attacking what they see as a 'foreign' body - the baby's cells. This happens when a mother has become sensitised to rhesus-positive cells, usually as a result of a previous pregnancy.

In worst case scenarios, it can result in the babies suffering brain damage or death.

An unusual antibody was found in Harrison's blood and in the 1960s, he worked with doctors to use the antibodies to develop an injection called Anti-D. Anti-D prevents the mother's body from developing the antibodies that would attack her baby.

Since then, Harrison has donated 1000 times - every batch of Anti-D in Australia has been made from his donations and it is estimated that two million babies have been saved since the vaccine was developed.

There are no more than 50 other people in Australia with the rare antibodies and soon doctors will be looking for someone to replace James.

Jemma Falkenmire, of the Australian Red Cross Blood Service says:

"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, James said that despite his long history of donating blood, it doesn't get any easier for him.

“Never once have I watched the needle go in my arm," he said. “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.”