News media has been utilized as a political tool to stray from facts, presenting biased claims without evidence. Amid the COVID-19 pandemic, politically biased news (PBN) has significantly undermined public trust in vaccines, despite strong medical evidence supporting their efficacy. In this paper, we analyze: (i) how inherent vaccine stances subtly influence individuals' selection of news sources and participation in social media discussions; and (ii) the impact of exposure to PBN on users' attitudes toward vaccines. In doing so, we first curate a comprehensive dataset that connects PBN with related social media discourse. Utilizing advanced deep learning and causal inference techniques, we reveal distinct user behaviors between social media groups with various vaccine stances. Moreover, we observe that individuals with moderate stances, particularly the vaccine-hesitant majority, are more vulnerable to the influence of PBN compared to those with extreme views. Our findings provide critical insights to foster this line of research.

翻译：新闻媒体曾被用作偏离事实的政治工具，传播缺乏证据的偏见性言论。在COVID-19疫情期间，尽管有强有力的医学证据支持疫苗有效性，政治化新闻仍显著削弱了公众对疫苗的信任。本文分析：（i）内在的疫苗立场如何微妙地影响个体选择新闻来源及参与社交媒体讨论的行为；以及（ii）接触政治化新闻对用户疫苗态度的影响。为此，我们首先构建了一个连接政治化新闻与相关社交媒体讨论的综合数据集。利用先进深度学习与因果推断技术，我们揭示了不同疫苗立场社交媒体群体间的差异化用户行为。此外，我们观察到持温和立场的群体（尤其是占多数的疫苗犹豫者）相较于极端观点者，更易受到政治化新闻的影响。本研究为推进该领域研究提供了重要启示。