Smallpox ranks among the world’s most terrible diseases. Over the centuries, it has killed or scarred hundreds of millions of people. It seems to have originated in the tropical zones of sub-Saharan Africa or India, and spread along trade routes to China and Europe. Virologists suspect that the disease was a mutation of a pox-like virus that afflicted domesticated animals.

Epidemics are recorded in ancient times, in the Middle Ages, and in the early modern period. But it was in the New World that it reaped its most deadly harvest. The disease decimated the native American populations of Mexico and Peru, and greatly assisted in the Spanish conquest. The Indians had developed no natural resistances to the disease, and were very nearly wiped out by it.

Experience with the disease had brought some progress in controlling it. In China and the Near East, it was known that exposing an uninfected person to smallpox scabs or pustules could act as some insurance from catching the disease. The Chinese method was to have a patient inhale a powder made from ground scabs; in the Middle East, a “wet” smallpox scab was rubbed into a cut in the person’s skin. This method came to be called “variolation,” a word derived from the medical term for the smallpox virus (variola).

Variolation was popularized in England and the American colonies through the efforts of Lady Mary Wortley Montagu, a former sufferer of the disease who managed to cure herself. She accompanied her husband to Constantinople in 1716 and observed doctors practice variolation on patients. After returning to England in 1718, she worked hard to have the practice adopted, but progress was slow.

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It seems strange to us today why it took so long for “obvious” medical treatments to become generally accepted, but it must be remembered that the medical field is an establishment like any other, with vested interests that can look on innovations with suspicion. We need only remember how long it took for the cure for scurvy to become recognized, despite the fact that sailors in the Middle East and India had been eating fresh citrus as a preventative for centuries.

There was a terrible outbreak of smallpox in Boston in 1721 that killed 15% of the population. The numbers would have been even worse had it not been for the efforts of Cotton Mather, a scholarly clergyman and amateur scientist. Mather personally vaccinated dozens of families, often at great physical risk to himself. The risk came not from the virus, but from attempted assaults on his person by uninformed people who distrusted the procedure.

But it would be Edward Jenner who finally brought the disease to heel. He did not “invent” vaccination, but he did figure out a new and improved way of administering it. Jenner’s discovery began, like many great discoveries, with an observation that not many had thought much of.

Jenner was a maverick country doctor and a man of many interests. He noticed that milkmaids in Gloucestershire often contracted a mild infection called cowpox from rubbing the nipples of lactating cows. Once the maids had cowpox, they never contracted smallpox. Could there be some connection between these two facts?

Jenner believed there was. The idea came to him that if he infected a patient with the mild cowpox, he could thereby safeguard them from the deadly smallpox. But proving this was another matter. Jenner did not have an advanced knowledge of the immune system or virology. He had intuition and conviction, and these proved to be enough.

In a risky procedure (done apparently without his patient’s consent), Jenner infected an eight-year old boy named James Phipps with cowpox. He took a drop of fluid from a cowpox scab on the wrist of a milkmaid named Sarah Nelms, and rubbed it on the skin of his test subject Phipps.

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He noticed the appearance of the disease, but it went away in about ten days. He then infected the boy directly with smallpox. And nothing happened. “Several months afterwards,” he wrote in a paper published in 1798, “he was again inoculated with variolous matter, but no sensible effect was produced in the constitution.”

So the procedure worked. Jenner did receive some castigation for his human experiments, but the criticism subsided when the results began to become evident. Jenner’s method was much more efficient and practical than the old ones. Parliament in 1802 and 1807 funded him lavishly, and he set about eradicating the disease in England.

Smallpox practically vanished in Europe and America soon after, and its control is practically taken for granted in the modern era. Jenner’s discovery was relevant not only in controlling smallpox, but also for the practice of vaccination in general.

In May 1980, the World Health Organization formally certified smallpox as “eradicated.” This feat was due largely to the techniques pioneered by Jenner. We should note that eradication of a disease is not a permanent condition. If future generations fail to heed the lessons of the past, they will find smallpox—“the speckled monster”—more than willing to return.

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