Following the signing of a treaty with Japan in 1876, Joseon entered a new international context shaped by the opening of its ports. Through the diplomatic missions dispatched to Japan, Joseon was exposed—albeit indirectly—to Western culture that had already been filtered through Japanese interpretations. This influx of Western knowledge, especially in the sciences, precipitated significant transformations within Joseon society. Among the most notable was the formal introduction of the cowpox vaccination method (udu, 牛痘).Although the technique had been briefly introduced during the late Joseon period by scholars such as Jeong Yak-yong, it was through the persistent efforts of Ji Seok-yeong that cowpox vaccination gradually gained traction in Joseon. Ji initially acquired the method at the Jesaeng Hospital in Busan and subsequently deepened his understanding during a stay in Japan. Upon his return, he actively engaged in cowpox inoculation and began consolidating his knowledge into a systematic form, culminating in the compilation of Udusinseol (牛痘新說, New Treatise on Cowpox), as indicated in his autobiographical work Yuyudang Gobaek.Admittedly, Udusinseol was primarily a compendium of selected arguments extracted from various sources, including Jungseomungyeonrok (中西聞見錄), Buyoungsinseol (婦嬰新說), Mangukgongbo (萬國公報), Jongdugwigam (種痘龜鑑), and Yindoulüe (引痘略). Nevertheless, the criteria Ji employed in selecting and arranging these discussions reflect his own perspective on cowpox vaccination. Notably, he rejected superstitious interpretations of smallpox and intentionally omitted central claims found in Yindoulüe, despite its considerable influence in the dissemination of variolation practices across East Asia. Specifically, he excluded the theory that smallpox originated from prenatal toxins (taedok, 胎毒) and the assertion that the Triple Burner meridian (samchokyeong, 三焦經) was a crucial site for inoculation. Instead, he limited his citations from Yindoulüe to prescriptions for treating post-vaccination symptoms.At the same time, Ji appears to have recognized the necessity of transforming public perceptions in order to promote the cowpox method in a society where variolation remained deeply entrenched. This challenge had also been identified by earlier figures such as Dudgeon, Hobson, and Qiu Xi, all of whom had worked to disseminate knowledge of cowpox. From the writings cited by Ji Seok-yeong, three principal advantages of the cowpox method are emphasized: Cowpox vaccination is significantly safer than variolation. It provides complete and lasting immunity. The associated cost is remarkably low.
S. B. Kim (Sun,) studied this question.