Policy Events, Emotional Fluctuations, and Vaccination Behavior: A Longitudinal Analysis of Public Opinion on HPV Vaccines in China

Cervical cancer, mainly caused by high-risk HPV infection, is the fourth most common cancer among women worldwide. From the approval of the bivalent HPV vaccine in 2016 to its inclusion in the national immunization program in 2025, China's HPV vaccine policy has completed a full cycle, but long-term public opinion tracking research remains insufficient. This study collected and cleaned 15,391 related posts from Zhihu, Weibo, Baidu Tieba, and Xiaohongshu, and used the LDA thematic model and sentiment dictionary analysis to measure vaccine hesitancy using an A2P ratio. The results show that public discussion has evolved from infection risk awareness to comprehensive prevention, and then to post-vaccination management; The A2P ratio dropped from 0.92 to 0.51, and the proportion of positive posts rose from 21.3% to 38.5%. After the Changchun Changsheng incident in 2018, positive sentiment dropped to 45.5%, but later rebounded to 58.1% with policy expansion. The "Policy/Event → Emotional → Vaccination Behavior" analytical framework provides empirical support for evidence-based vaccine communication strategies. In the future, multimodal data and individual tracking surveys should be integrated to deepen attitude-behavior pathway research.