Vaccination is one of the most impactful healthcare interventions in terms of lives saved at a given cost, leading the anti-vaccination movement to be identified as one of the top 10 threats to global health in 2019 by the World Health Organization. This issue increased in importance during the COVID-19 pandemic where, despite good overall adherence to vaccination, specific communities still showed high rates of refusal. Online social media has been identified as a breeding ground for anti-vaccination discussions. In this work, we study how vaccination discussions are conducted in the discussion forum of Mumsnet, a United Kingdom based website aimed at parents. By representing vaccination discussions as networks of social interactions, we can apply techniques from network analysis to characterize these discussions, namely network comparison, a task aimed at quantifying similarities and differences between networks. Using network comparison based on graphlets -- small connected network subgraphs -- we show how the topological structure vaccination discussions on Mumsnet differs over time, in particular before and after COVID-19. We also perform sentiment analysis on the content of the discussions and show how the sentiment towards vaccinations changes over time. Our results highlight an association between differences in network structure and changes to sentiment, demonstrating how network comparison can be used as a tool to guide and enhance the conclusions from sentiment analysis.

翻译：疫苗接种是在给定成本下挽救生命最多的医疗干预措施之一，这使得反疫苗运动被世界卫生组织列为2019年全球健康的十大威胁之一。在COVID-19大流行期间，这一问题的重要性进一步凸显——尽管整体疫苗接种依从性良好，但特定群体仍表现出较高的拒绝率。在线社交媒体已被确定为反疫苗讨论的温床。本研究考察了Mumsnet（一家面向家长的英国网站）讨论论坛中疫苗接种讨论的开展方式。通过将疫苗接种讨论表征为社会交互网络，我们能够应用网络分析技术来刻画这些讨论，特别是网络比较——一项旨在量化网络间相似性与差异性的任务。基于图元（graphlets，即小型连通网络子图）的网络比较方法揭示了Mumsnet上疫苗接种讨论的拓扑结构随时间变化的特征，尤其在COVID-19前后的差异。我们还对讨论内容进行了情感分析，展示了疫苗接种相关情感随时间的变化。研究结果凸显了网络结构差异与情感变化之间的关联，证明网络比较可作为引导和强化情感分析结论的有效工具。