Some diseases can be transmitted from one person to another person or from other sources to humans. These “transmissible” diseases include HIV/AIDS, tuberculosis, malaria, measles, pertussis/whooping cough, syphilis, Hepatitis B, pneumonia, influenza, a host of tropical diseases, and smallpox, .
Fortunately, the human body has a defense system called the immune system. Unfortunately, it isn’t always strong enough to resist diseases, especially “new” diseases that a community has not encountered before. The body has to develop immunities over time. For thousands of years, people have known that people who have been sick with a disease and survived, then don’t catch it again in the future. They are immune.
Sometime between 900 and 1000 AD, a Chinese doctor wondered if giving somebody a very mild case of an infectious disease could make them immune to the more severe version. Basically, make a small cut, pour in some infected material, bandage up the cut, and wait for the patient to get not-as-sick. Over time, this important knowledge migrated westward from China to India to the Ottoman Empire in the Middle East.
From 1716 to 1718, Sir Edward Wortley-Montagu (1678-1761)—a very rich British aristocrat—served as ambassador in the Ottoman Empire. He took along his wife, Lady Mary Wortley-Montague. She was beautiful, intelligent, and very independent minded. Her younger brother had died of smallpox and she had lived through a case herself. When she accompanied her husband to Istanbul, her inquiring mind vacuumed-up information. One thing she picked up was that the Turks had a method for preventing full-blown smallpox. She had it applied to their young son. Back in England, she became a strong advocate for this method, called inoculation.
It didn’t catch on entirely because the risk of developing full-blown smallpox. Then, in 1796, Dr. Edward Jenner tried inoculating a patient with the related, but far less dangerous, disease called cowpox. This worked very well without running any grave risks. The Latin word for cow is “vacca,” so Jenner’s method came to be called “vaccination.”
In the 20th Century, the American medical researcher, Dr. Maurice Hilleman (1919-2005) discovered vaccines for forty diseases. He saved more lives than any medical researcher in the Twentieth Century. For much of his career, he worked for Merck in Montgomery County, Pennsylvania.
Since 1945, the World Health Organization of the United Nations has sponsored vaccination programs around the world. Especially in the “developing world” these efforts have massively reduced childhood deaths. In 1990, there were 93 deaths per 1000 live births; in 2017, there were 39 deaths per 1000 live births. If you don’t want to do the math yourself, this is 1 in 11 children dying before reaching age 5 in 1990; versus 1 in 26 children dying before reaching age 5 in 2017. Anyway you cut it, this is a great story of human progress. Not that it will appear on the nightly news.
 When my Dad was in the Army, guys with syphilis used to say that they must have caught the disease in a bathroom. Doctors often asked “Wasn’t the tile floor cold?”
 The powdered scab of smallpox patients, for example. I never said it would be pretty.
 Including those for measles, mumps, chickenpox, influenza, pneumonia, meningitis, and Hepatitis A and B.
 See: “The Man Who Saved a Billion Lives.”