Stance and Engagement: How Community Notes Influence HPV Vaccine Conversations on X in Japan

This study examines the impact of Community Notes on users' stance and posting behavior regarding the human papillomavirus (HPV) vaccine on X. Unlike previous research focusing on affected posts and authors, this study analyzes users who viewed Community Notes and their posting behavior before and after exposure. We analyzed posts related to the HPV vaccine using X's official Community Notes dataset (January 2021–July 2024). Posts were classified as "Support," "Oppose," or "Neutral" using a large language model (GPT-4o, OpenAI), and changes in stance and posting frequency were evaluated. Findings show that 73% of users maintained their stance after viewing Community Notes. However, posting frequency increased sharply immediately after the note was added, especially among opposing users. This suggests that, since most Community Notes support vaccination, opposing users may have actively responded by posting critical responses. This study contributes by examining viewer behavior, not just post authors. However, limitations include GPT-4o's classification accuracy and the restricted scope of topics and users covered in this study. Future research should improve the evaluation of Community Notes by verifying users who viewed Community Notes and enhancing stance classification through better prompts and model comparisons. Additionally, expanding the analysis beyond the HPV vaccine will help assess the broader applicability of the findings.