Topic Shifts and Source-Type Differences in Weibo Discourse Surrounding the Inclusion of HPV Vaccination in China’s National Immunization Program

Background: To examine changes in HPV vaccine-related Weibo discussion topics and differ-ences across account types around the announcement and stipulated implementation of China's policy to include HPV vaccination in the National Immunization Program, providing insights into communication priorities at different stages of implementation. Methods: This retrospective be-fore-and-after observational study included 8,916 original HPV vaccine-related Weibo posts pub-lished between 30 April 2025 and 30 April 2026. The policy announcement (30 October 2025) and stipulated implementation date (10 November 2025) were used to define the study periods. Latent Dirichlet allocation (LDA) was used to identify topics, while chi-square tests and multinomial lo-gistic regression examined differences in topic distributions. Results: Topic modeling identified four topics: cervical cancer screening and disease risk, population protection and health awareness, free vaccination policy and eligibility, and vaccine supply and domestic production. Topic distri-butions differed significantly before and after the policy announcement (χ² = 1349.101, df = 3, P < 0.001; Cramér's V = 0.389). The proportions of posts concerning cervical cancer screening and disease risk and free vaccination policy and eligibility increased from 14.86% to 34.05% and from 8.80% to 25.02%, respectively, while population protection and health awareness declined from 48.32% to 17.09%. Between the announcement and stipulated implementation date, free vaccina-tion policy and eligibility accounted for 53.16% of posts, declining to 17.03% thereafter, whereas cervical cancer screening and disease risk increased to 39.19%. A significant interaction was ob-served between policy period and account type (likelihood-ratio χ² = 76.142, df = 9, P < 0.001). Conclusion: Weibo discussion topics showed stage-specific changes around the policy announce-ment and stipulated implementation date, with variations across account types. Social media mon-itoring may help identify communication priorities and inform health communication strategies during immunization program implementation. However, these findings cannot establish popula-tion-level attitudes, vaccination behavior, or causal policy effects.