Infectious Diseases: Meet a Scientist

Did you get your vaccinations when you were younger? Why do you have to get vaccinated? It hurts. But the hurt is minor compared to the diseases you might get if you weren’t vaccinated. Vaccinations can help you resist infections.

Have you heard about smallpox? Smallpox is a viral disease like chickenpox, which you probably have heard of. Maybe you or some of your friends even got infected with chicken pox.

Smallpox is caused by a virus that is both highly infectious (infects readily) and very contagious (spreads easily). Smallpox once was a major worldwide scourge for many centuries. You are about to read the story of how vaccination eliminated smallpox from the entire world.

For centuries, people around the world lived in dread of smallpox because there was no treatment and the disease was so deadly. About 30% of those infected with smallpox died.

Until Edward Jenner came along, the idea of vaccination against diseases like smallpox was unknown. Many people recognized that those who recovered from some diseases seemed resistant to infection a second time (acquired immunity). However, few people had no concept of vaccination.

Because smallpox was so common and deadly, once a vaccine was developed, a worldwide campaign to eliminate the disease began. A smallpox vaccine was initially developed in 1796. Because almost everybody was vaccinated, smallpox was eliminated worldwide by 1972.

In this “Meet the Scientist” segment, you will read the story of this deadly disease and how a physician, Edward Jenner discovered a vaccine against it.

Meet the Scientist,



By the late 1700s, a British physician named Edward Jenner (Figure 1) discovered a way to prevent smallpox infections. The prevention involved inventing the principle of vaccination. This earned Jenner the title of “father of immunology.” Still, despite his important discovery, Jenner had no way of knowing just how vaccinations work. Those mechanisms were only discovered in the 20th century!

Edward Jenner was born in Gloucestershire, England on May 17, 1749, the son of the pastor of a local church. As a boy Edward became interested in medicine. At the age of 14, he was apprenticed to a local surgeon and later trained in London. Nine years later in 1772, he returned to his hometown, where he spent most the rest of his career as a physician.

Gloucestershire was a small rural town surrounded by farms. Dairy farmers in the area noticed that their cows sometimes caught a disease known as “cowpox.” Jenner, sometimes serving as a veterinarian, saw many cases of cowpox and even noticed that sometimes milk maids got cowpox on their hands. This disease caused pox-like lesions in cows, especially on their udders and teats (Fig. 3). Many decades later, scientists discovered that cowpox was a virus related to smallpox.

Of course, in that era, no one knew about viruses. Even the idea that germs could cause disease had not yet been established. That came about 100 years later from the work of Louis Pasteur. Even so, doctors in the 1700s knew there were diseases that could be spread from animals to animals, from animals to humans, and from humans to humans. Cowpox and smallpox were among such diseases.

Human smallpox was common in Jenner’s era. Physicians in those days recognized that survivors of smallpox infections could become forever resistant to reinfection. They also knew from the work of a Dutch physiologist, Jan Ingenhaus, that pressing a small amount of pus from a smallpox lesion into a small wound of a healthy person conferred later resistance in those that it did not kill. Dr. Jenner knew from local folklore that milkmaids who had been infected by cowpox never seemed to become infected with smallpox.