Koyama Shisei (Japanese:小山 肆成; 1807-1862) was a Japanesephysician and vaccinologist. He also used the nameHōshū (蓬洲).

Koyama's reputation was such that he was compared with other outstanding scientists of his time, as in the phrase, "Seishū of the north, Hōshū of the south" (北の青洲、南の蓬洲).

He was born in 1807 near Hisagi (久木) village in ruralKii Province to ajizamurai family. When he was young, he traveled toKyoto to study with his elder brother Koyama Fumiaki (小山 文明), but Fumiaki "died suddenly in a fit of rage" (憤死) in 1822.^[1] In 1823, he began studyingConfucianism under his brother's teacher Okada Nangai (岡田 南涯), and medical science under Takagai Ki'en (高階 枳園), a physician to theImperial Court. He also studiedherbal medicine andkanpō. Eventually, Koyama opened his own medical practice onKarasuma Street.^[2]

At the beginning of the 19th century, theBalmis Expedition introducedEdward Jenner's technique of usingcowpox to inoculate patients againstsmallpox toQing China. Hearing of this, Koyama obtained from Takagai Ki'en a copy of the Chinese bookYin dou lue (引痘略,Intōryaku) written byQiu Xi (邱 熺) which contained an explanation of Jennerian inoculation.^[2] Koyama's activities are primarily responsible for this information becoming widely available in Japan.^[3]

During theTenpō famine (1833–1837), an epidemic of smallpox ravaged Koyama's native Kii Province. After he learned that his nephew's entire family had died of smallpox in 1835, he immersed himself in research to discover a way to combat the disease.^[2][1] Koyama sold almost all of his personal belongings, including his family swords, in order to raise money to buycattle for his research. The cattle were used to cultivate cowpox samples.^[3]

In 1849, Koyama successfully tested Japan's first Jennerian smallpox vaccine, Gyūkajintōbyō (牛化人痘苗).^[2]

Koyama died in Kyoto in 1862.^[2]

• Kuwata Ryūsai (1811-1868)
• Fukase Yōshun
• Isao Arita

• Jannetta, Ann (May 23, 2007).The Vaccinators: Smallpox, Medical Knowledge, and the 'Opening' of Japan. United States: Stanford University Press.ISBN 978-0804754897.
• 山本 Yamamoto, 亨介 Kyōsuke (1994).Shutō-i Koyama Shisei no shōgai 種痘医小山肆成の生涯 (1st ed.). Japan: 時事通信社 Jiji Tsūshinsha.ISBN 4788794403.

• 1807 births
• 1867 deaths
• 19th-century Japanese physicians
• Japanese medical researchers
• Samurai
• Vaccinologists
• Scientists from Wakayama Prefecture

• Articles containing Japanese-language text