Contents of Japanese pro- and anti-HPV vaccination websites: A text mining analysis

•We showed 16 frequently appearing contents on pro- and anti-HPV vaccination websites.•Side effects most frequently appeared on both pro- and anti-HPV-vaccination websites.•Preventable effect and cause of cervical cancer followed on pro websites.•Toxicity of vaccine and girls who suffer from side effects followed on anti websites. In Japan, the human papillomavirus (HPV) vaccination rate has sharply fallen to nearly 0% due to sensational media reports of adverse events. Online anti-HPV-vaccination activists often warn readers of the vaccine’s dangers. Here, we aimed to examine frequently appearing contents on pro- and anti-HPV vaccination websites. We conducted online searches via two major search engines (Google Japan and Yahoo! Japan). Targeted websites were classified as “pro,” “anti,” or “neutral” according to their claims, with the author(s) classified as “health professionals,” “mass media,” or “laypersons.” We then conducted a text mining analysis. Of the 270 sites analyzed, 16 contents were identified. The most frequently appearing contents on pro websites were vaccine side effects, preventable effect of vaccination, and cause of cervical cancer. The most frequently appearing contents on anti websites were vaccine side effects, vaccine toxicity, and girls who suffer from vaccine side effects. Main disseminators of each content according to the author’s expertise were also revealed. Pro-HPV vaccination websites should supplement deficient contents and respond to frequent contents on anti-HPV websites. Effective tactics are needed to better communicate susceptibility to cervical cancer, frequency of side effects, and responses to vaccine toxicity and conspiracy theories.