Fluoride in the water

Grand Rapids, Michigan, 1945: first city to add fluoride to its water supply.

It works on everyone in the city, whether or not they brush, floss, or have a dentist.

Seatbelts

Required in new cars from 1968. New York passed the first law requiring you to actually wear one in 1984.

The safety belt was not the invention. The law was.

Telling people cigarettes kill

1964: the Surgeon General's report linked smoking to lung cancer. It was front-page news.

There was no drug and no surgery. A report, then warning labels, taxes, and ad bans did the work.

Vaccines

Smallpox killed an estimated 300 million people in the 20th century. Last natural case: 1977. Declared gone: 1980.

Polio in the U.S., 1952: about 21,000 kids paralyzed in one year. Vaccine in 1955. Zero U.S. cases since 1979.

Smallpox is the only human disease ever eradicated. The tools were a vaccine and decades of coordinated case tracking.

Clean water

London, 1854. John Snow maps cholera deaths, finds they cluster around one pump on Broad Street, and has the handle removed.

U.S. cities start filtering and chlorinating water around 1908. Typhoid deaths fall from ~30 per 100,000 to almost zero by 1950.