Müller contributed in the research effort into hepatitis B and development of a vaccine, in addition, he became the Vice President of Beijing Medical University in China.
At the University of Basel, he met a Chinese student named Chiang Zhaoxian, who told Müller about China, its culture, history and ongoing events.
[1] Hans Müller left Switzerland in April 1939 after receiving his doctorate and traveled to Hong Kong via Marseille.
During June and July of the same year, he made his way to Yan'an via Nanning, Guiyang, Chongqing, Chengdu, Baoji, and Xi'an.
The further stages of his career were an appointment as Professor at the Shenyang Medical College, where he later served Dean and head of pediatrics, an appointment as Professor of Internal Medicine at Beijing's Jishuitan Hospital, and finally vice president of Beijing Medical University.