Jenner's vaccine

The story

A disease that marked lives

Until two centuries ago, one of humankind's greatest fears was smallpox. It was a highly contagious disease caused by a virus: it brought a high fever and covered the body in painful pustules. About one in three people who caught it died; those who survived carried the marks for the rest of their lives, scars on the face, and sometimes were left blind. In the 18th century in Europe smallpox killed hundreds of thousands of people every year, especially children. Kings and queens were not safe: many died of it, among them Louis XV of France.

It was already known that anyone who survived smallpox did not catch it again. For centuries, in China, India and Africa, people had tried to make use of this fact with “variolation”: the skin of a healthy person was scratched with a little material taken from someone with a mild case. That way they caught a lighter form of the disease and stayed protected. In 1721 an English noblewoman, Lady Mary Wortley Montagu, who had seen the practice in Constantinople, had her daughter inoculated and promoted the method in England. It was a risky method, though: a small share of those who were variolated became seriously ill, and could infect others.

The milkmaids

Edward Jenner was born in 1749 at Berkeley, a village in the west of England, the son of a vicar. He became a country doctor. When he was a boy, so the story goes, a milkmaid told him: “I can't catch smallpox, because I've had cowpox”. Cowpox was a mild disease of cows, which could pass to the hands of the people who milked them, causing a few pustules. In the countryside it was said that anyone who had caught it was protected from real smallpox, but nobody had proved it.

Jenner, who was curious and methodical, spent years observing his patients, collecting cases and asking questions. He was a friend of John Hunter, a great surgeon who had taught him an important principle: don't just think, try things and run experiments.

14 May 1796

On 14 May 1796 Jenner carried out his test. A young milkmaid, Sarah Nelmes, had cowpox pustules on her hand, which she had caught from a cow called Blossom. Jenner took a little fluid from a pustule and, with a small scratch, put it into the arm of James Phipps, an eight-year-old boy, the son of his gardener. The boy had a mild fever and a few pustules, and recovered in a few days.

On 1 July Jenner carried out the decisive test: he inoculated James with material from real smallpox. The boy did not fall ill: he was protected. Jenner repeated the experiment with others, and in 1798 he published the results in a book. The method was called “vaccination”, from the Latin “vacca”, meaning cow. Today we know that this test would be forbidden, because it was done on a child without the safety guarantees that are now compulsory; but at the time it opened the way to one of the great achievements of medicine.

A discovery that travels

Vaccination spread quickly. There were sceptics, and cartoonists who drew people with cow horns, but the results were plain to see. In 1800 in Milan the doctor Luigi Sacco began to vaccinate and spread the vaccine across Italy. Napoleon had his soldiers vaccinated. In 1803 a Spanish expedition, led by Francisco Balmis, set out with twenty-two orphans as “carriers” of the vaccine: since there was no way to keep it, they were infected one after another in turn during the crossing, in order to bring the vaccine to the Spanish colonies in America and Asia.

The eradication of smallpox

During the 19th century vaccination became compulsory in many countries. In 1967 the World Health Organization launched a worldwide campaign to eliminate smallpox, with teams that searched for the sick and vaccinated those around them, in remote villages in Africa and Asia. The last natural case was in Somalia, in 1977. On 8 May 1980 the WHO declared smallpox “eradicated”: it is the only human disease wiped from the Earth.