The HPV vaccine is an immunization to prevent human papillomavirus (HPV) infection spread through sexual intercourse. Public opinion on the HPV vaccine in Japan is changing dramatically. Social media, the primary modern forum for exchanging ideas, has become a forum for both enlightenment and skepticism as opinions about vaccination are widely discussed. In this paper, we selected a sample data set based on 3.97 million Japanese tweets about the HPV vaccine posted on Twitter(X) from 2011 to 2021 and analyzed the retweet network. The results revealed structural connections and communication patterns among different opinion groups. Specifically, we found that connections tended to be divided according to the extremes of opinion, and that groups with intermediate opinions were most likely to function as intermediaries. Although the large-scale network analysis is still a work in progress, it offers important implications for the design of science communication strategies on social media.
