In this work, we study English-language vaccine discourse in social media posts, specifically posts on X (formerly Twitter), in seven years before the COVID-19 outbreak (2013 to 2019) and three years after the outbreak was first reported (2020 to 2022). Drawing on theories from social cognition and the stereotype content model in Social Psychology, we analyze how English speakers talk about vaccines on social media to understand the evolving narrative around vaccines in social media posts. To do that, we first introduce a novel dataset comprising 18.7 million curated posts on vaccine discourse from 2013 to 2022. This extensive collection-filtered down from an initial 129 million posts through rigorous preprocessing-captures both pre-COVID and COVID-19 periods, offering valuable insights into the evolution of English-speaking X users' perceptions related to vaccines. Our analysis shows that the COVID-19 pandemic led to complex shifts in X users' sentiment and discourse around vaccines. We observe that negative emotion word usage decreased during the pandemic, with notable rises in usage of surprise, and trust related emotion words. Furthermore, vaccine-related language tended to use more warmth-focused words associated with trustworthiness, along with positive, competence-focused words during the early days of the pandemic, with a marked rise in negative word usage towards the end of the pandemic, possibly reflecting a growing vaccine hesitancy and skepticism.

翻译：本研究针对社交媒体（特别是X平台，原Twitter）上关于疫苗的英文讨论帖文，分析了COVID-19疫情爆发前七年（2013年至2019年）与疫情首次报告后三年（2020年至2022年）的话语演变。借鉴社会心理学中的社会认知理论与刻板印象内容模型，我们解析了英语使用者在社交媒体上谈论疫苗的方式，以理解疫苗相关叙事在社交帖文中的动态变化。为此，我们首先构建了一个新颖的数据集，包含2013年至2022年间1,870万条经过筛选的疫苗讨论帖文。该大规模数据集通过严格的预处理从初始的1.29亿条帖文中提炼而成，涵盖了疫情前与疫情时期，为探究英语X平台用户对疫苗认知的演变提供了重要依据。分析表明，COVID-19大流行导致X用户对疫苗的情感态度与话语表达发生复杂转变。我们观察到，疫情期间负面情绪词汇的使用有所减少，而惊讶与信任相关情绪词汇的使用显著增加。此外，在疫情初期，疫苗相关语言更倾向于使用与可信赖性相关的温暖导向词汇，以及积极的能力导向词汇；但在疫情后期，负面词汇的使用明显上升，这可能反映了日益增长的疫苗犹豫与怀疑情绪。