This article explores imperial Japan’s response towards an influenza pandemic from 1918-1921 and details the establishment of public health policies in imperial Japan by tracing the evolution of preventive measures in its colonies, especially in the colonial Korea, where the influenza pandemic was prevalent to a degree similar to Japan. In contrast to other Western countries, Japan identified that influenza had been continuously prevalent over the course of three years and implemented preventive measures in the Japanese metropole and its colonies until 1921.

In colonial Korea, preventive measures were initially aimed at protecting the throat through gargling, and later included vaccinations in addition to measures related to improving personal hygiene, education around the risks of influenza, and mask wearing. Also, the authorities tried to implement measures equivalent to those for notifiable diseases. However, these preventive measures may have had only a limited effect because the policy lacked enforcement, it was difficult to determine the cause of disease, and the vaccine efficacy had not been sufficiently proven. However, one significant change over previous responses to influenza prevalence was that the authorities were now able to directly engage with personal hygiene measures over a sustained period of three years in the name of protecting and improving public health. This in turn, led to the development of a set of detailed guidelines for public health controls. This, in turn may have influenced subsequent revisions of the Infectious Disease Prevention Act in Japan in 1922.