Vaccination Day

What Is Vaccination Day?

Every May 14th is "Vaccination Day" (種痘記念日, Shutō Kinenbi) in Japan. On May 14, 1796, English physician Edward Jenner performed the first vaccination — inoculating 8-year-old James Phipps with material from a cowpox sore on the hand of milkmaid Sarah Nelmes to protect him from the far more dangerous smallpox. Jenner's work — the principle that exposure to a mild related disease could confer immunity against a more dangerous one — was one of the most consequential medical discoveries in human history, ultimately leading to the eradication of smallpox and the development of vaccines for many other diseases.

Edward Jenner and the Discovery of Vaccination

Edward Jenner (1749–1823) built on the observation that milkmaids who had caught cowpox appeared to be immune to the far more deadly smallpox. After inoculating young Phipps with cowpox, he later exposed him to smallpox and found that the boy did not develop the disease. Before this, "variolation" — inoculation with material from smallpox patients — had been practiced, but it carried a real risk of serious illness. Jenner published his findings in 1798; despite early opposition, vaccination spread rapidly through Europe and beyond. Jenner found a working solution long before the germ theory of disease or the immune system was understood.

Vaccination in Japan

Smallpox vaccination became established in Japan in 1849, when Otto Mohnike, a physician at the Dutch trading post, brought cowpox vaccine to Nagasaki. That same year, the physician Ogata Kōan and others opened the Joutōkan (除痘館), a vaccination center in Osaka, and helped spread the practice across the country. Today, Japan runs a routine immunization program covering childhood vaccines as well as seasonal vaccines such as influenza.

Vaccination and Modern Public Health

Vaccination is regarded as one of the most cost-effective public health measures ever developed — responsible for eradicating smallpox (1980) and dramatically reducing polio, measles, and diphtheria. The word "vaccine" itself comes from the Latin "vacca" (cow), a reminder of Jenner's use of cowpox; Louis Pasteur later proposed extending the term to all preventive inoculations.

Fun Facts

• Smallpox eradication: The WHO declared smallpox eradicated on May 8, 1980 — the only human disease to have been eradicated so far. Japan's routine smallpox vaccination was effectively discontinued in 1976, so many people who grew up before then still have a small vaccination scar on their upper arm.
• Satirical cartoons: In the early 1800s, British cartoonists mocked vaccination with images of cows sprouting from the bodies of vaccinated people — a reminder of how new medical ideas can meet resistance.
• Remaining virus stocks: Smallpox virus samples are still kept for research under strict control at designated laboratories in the United States and Russia.