The Protestant mission in Korea was also initiated by doctors. Horace N. Allen, a medical missionary, was sent to Korea as a resident for the first time in September 1884 by the Board of Foreign Mission of the Northern Presbyterian Church in the U.S. and later founded the Chejungwon (House of Universal Helpfulness, here after), which was the first Westernized medical hospital in Korea. Following Allen, H.G. Underwood, who came to Korea in April 1885, was a clergyman but served as a teacher at the House of Universal Helpfulness. J.W. Heron, C.C. Vinton, and L.S. Horton who came to Korea thereafter were all medical missionaries. W.B. Scranton, the first Korea-residing Methodist missionary sent by the Mission Society of the Northern Methodist Episcopal Church was also a medical missionary. The Church of England and the Presbyterian Church of Canada and several other Churches sent medical missionaries to Korea during the early stage of Protestant mission. Their purpose of coming to Korea was to spread the Gospel message of Christianity through their medical practice.

The greatest benefactor of medical missions conducted in Korea was Oliver R. Avison (1860–1956). He abandoned his stable job as a professor with the School of Medicine at the University of Toronto to come to Korea as a medical missionary in 1893. In the early stage when the Western medical techniques were spread in Korea, he established a hospital equipped with proper facilities in Seoul and gave quality medical education. Until he returned to his home in 1935, he devoted himself to Korea over two generations for 43 years. He was the actual founder of Westernized, modern medicine in Korea. He brought about a revolution of modernized and westernized hospitals and medical education, which had been little more than names during the first stage of Western medical mission in 1885-1893. The House of Universal Helpfulness was jointly operated by the Joseon government and missionaries at first, but under the leadership by Avison the hospital was reformed as a hospital run by the Mission Board and Korea Mission only. He developed the House of Universal Helpfulness, which consisted of traditional Korean-style houses, into Severance Hospital equipped with the most modern facilities with the western style building in the history of modern Christian medical mission. The medical school of the House of Universal Helpfulness was expanded to become Severance Union Medical College in which missionaries from a number of denominations participated in medical education. With this renovation, he hardened the foundation for continuous development. Likewise, he suggested a new mission theory that was effective in medical mission efforts across the globe based on what he experienced as a main figure in the medical mission field in Korea. With his theory, vision, and effort, Severance Hospital, its medical school, and its nursing school laid the foundation for Korean medical education and produced countless doctors and nurses. On this background, Yonsei University Health System has become an institution that represents the history and development of the world medical mission in the 20th century.

Avison recognized the medical mission was not an indirect mission but mission itself as Underwood believed education was the mission itself. In the aspect that teaching and healing were part of the achievements of Jesus Christ, he saw that relieving pains of patients and teaching people themselves was the missionary work that spread the love of God. With this mission philosophy, he served as Director of the House of Universal Helpfulness for 6 years, and he developed his unique medical mission theory and presented his work at the 1900 Ecumenical Missionary Conference in New York. It was the first international Ecumenical missionary meeting in Protestant church. The President of U.S. Benjamin Harrison and other worldly renowned figures were attended. Avison's presentation was held on April 27th at the Carnegie Hall in New York. The title of his speech was “Comity in Medical Missions.”1

First, Avison raised cooperation among medical missions. Specifically, he insisted that it would have much greater effect if medical missionaries sent from each denomination were united to establish a hospital equipped with the best facilities rather than acting independently in a small hospital with incomplete facilities. The theological foundation of this argument was the ecumenical theology. He considered that the most of the denominations fundamentally believed in one God, one Lord, and one Holy Spirit, and he asserted that they should be united to overcoming denominational differences. He devoted his whole life to this ecumenical union spirit.

Second, he insisted on the establishment of hospital as an annex to medical college and development of hospital and medical school at the same time. To ensure that the two institutions developed at the same time, a medical college must be established. He argued that because the Mission Board could not send many doctors, it was necessary to foster native doctors in the mission field to replace the missionaries. Therefore, he perceived that mission societies should transcend their denominations and join together to foster native medical specialists, so that those native doctors could continue the supply of medical staff for hospital operation and medical education. By this way, it would be possible to sustain the medical mission.

Third, he proposed the transferring of mission hospitals to the native people. He kept in mind that the mission would be finished at some point and missionaries would have to leave. Thus, he believed that the hospitals and medical schools run by the missionaries must have the ability to be independent in many ways, including finance and management, and to do so, they must transfer the hospitals and institutions for training health care providers to the native people. In this sense, he trusted the native people, handed down his medical techniques, and trained them as best he could.

Avison practiced his theories on medical missions to prove the effectiveness thereof. L.H. Severance sympathized with his idea of the united medical mission presented in the 1900 New York Ecumenical Missionary Conference, and showed his favor to it. Severance decided to donate a fund to establish a new hospital in Korea as a sacrifice to live as Christ, transcending denominations, national borders, and race. This was the decisive opportunity to help Korean modern medicine develop hospitals with the up-to-date facilities and high-quality medical education. The Severance family contributed about $50000 to realize the dream and ideals of Avison. At that time, the majority of the Korea Mission member missionaries opposed the establishment of a large-scale hospital and full-scale medical education, insisting that the money should be used to build a small hospital and that the rest of the money should be left for preaching the Gospel. Despite the objection, Avison with the support of the Mission Board and the will of the donor L.H. Severance was able to open a new modern hospital built outside Namdaemun on November 16, 1904. The hospital was named after the donor and began a fresh start, but Avison made clear that the hospital succeeded the spirit and tradition of the House of Universal Helpfulness as he announced the opening of the hospital. From that time, Severance Hospital has operated as the highest-level hospital in Korea, as well as in East Asia.

As a number of mission societies were united together and participated in the hospital's operation and education, the appearance and scale of the hospital were reformed and its internal stability was strengthened, which cemented Severance Hospital as the central institution of Korean medical education. When he retired in 1934, his son Douglas Avison wanted to succeed his father's position, but he did not pass it on to his son but instead it to Dr. Keung Seon Oh, a Korean doctor who was the representative of the Southern Presbyterian Mission Board for the Severance Medical College. With all his activities, he actually proved that his theory of medical missions was the most efficient way for the mission.

Upon the medical mission theory of Avison, Severance Hospital has continued to develop. The Christian mission hospitals that were established all over the world around the beginning of the 20th century are now mostly closed or undeveloped. The hospitals and medical school developed by Avison, however, have continued to develop, becoming a distinguished medical institution not only in Korea today but also in the world medical mission field. Moreover, Avison contributed not only to medical sectors but also other areas for the development of modern higher education in Korea. He served as the principal of both Severance Union Medical College and Chosen Christian College for 18 years, preparing the groundwork of the integration of Severance Union Medical College and Chosen Christian College. The two colleges and hospital have made considerable strides to become a successful case in the history of world mission.

Avison's activities in Korea and his influence for 43 years produced tremendous accomplishments unmatched in the history of world medical missions from the end of the 19th century to the early 21st century. Unfortunately, his achievement and theories have been unnoticed and neglected in Korea and overseas. To illuminate his life, accomplishments, contributions, and influences, ongoing research and publications on him should be continued in a systematic and integrated manner: he must be widely known. The Korean Church, Korea and the Korean people should reflect on the devotion and contributions Avison made to the medical circle and higher education in Korea, and continue in his spirit.