A Coruña, Spain, November 30, 1803.
It was cold in the harbor. A ship called the María Pita was ready to sail for America. On the dock there were sailors, doctors, boxes… and twenty-two small children, between three and nine years old.
Almost all of them were orphans. None of them really knew where they were going. But they were carrying something very valuable. Not in their suitcases. In their arms.
At that time, smallpox was one of the most terrible diseases in the world. Every year it killed hundreds of thousands of people, and many survivors were left with scars on their faces.
In 1798, an English doctor, Edward Jenner, published how a vaccine worked. But there was a problem: it did not last long outside the body, and a voyage by ship to America took weeks.
A Spanish doctor, Francisco Xavier de Balmis, had a strange and brilliant idea.
"The vaccine can travel alive," he explained. "Inside the children."
The plan worked like this: the doctor vaccinated two children. After a few days, a small blister appeared on each child's arm. With the fluid from that blister, he vaccinated two more children. And so on, week after week, like a chain.
If the chain broke, the mission was over.
Someone had to take care of those children. That person was Isabel Zendal, the director of the orphanage in A Coruña and the only woman on the expedition. Her own son was among the children.
The voyage was hard. There were storms, and many children were seasick. Some cried at night. Isabel fed them, told them stories and looked after them when they got sick.
First they stopped in the Canary Islands and then in Puerto Rico. When they finally reached Venezuela, Balmis checked the arms of all the children. He was very nervous. Only one child still had the vaccine.
Just one.
Balmis got off the ship and immediately vaccinated twenty-eight Venezuelan children. The chain was still alive.
From there, the expedition split in two. One group went south. The other, with Balmis and Isabel, went to Cuba and Mexico. According to Balmis, they vaccinated about one hundred thousand people in Mexico. In 1805, with twenty-six Mexican children, they crossed the Pacific Ocean to the Philippines.
In 1980, the World Health Organization declared that smallpox had been eradicated. And today, many consider Isabel Zendal the first nurse on an international health mission.
But the real heroes of this story had no uniform and no title. They were between three and nine years old. And they carried the vaccine across half the world… in their own arms.