Pro- and anti-vaccination users use social media outlets, such as Twitter, to join conversations about vaccines, disseminate information or misinformation about immunization, and advocate in favour or against vaccinations. These users not only share textual content, but also images to emphasise their messages and influence their audiences. Though previous studies investigated the content of vaccine images, there is little research on how these visuals are distributed in digital environments. Therefore, this study explored how images related to vaccination are shared on Twitter to gain insight into the communities and networks formed around their dissemination. Moreover, this research also investigated who influences the distribution of vaccine images, and could be potential gatekeepers of vaccination information. We conducted a social network analysis on samples of tweets with images collected in June, September and October 2016. In each dataset, pro- and anti-vaccination users formed two polarised networks that hardly interacted with each other, and disseminated images among their members differently. The anti-vaccination users frequently retweeted each other, strengthening their relationships, making the information redundant within their community, and confirming their beliefs against immunisation. The pro-vaccine users, instead, formed a fragmented network, with loose but strategic connections that facilitated networking and the distribution of new vaccine information. Moreover, while the pro-vaccine gatekeepers were non-governmental organisations or health professionals, the anti-vaccine ones were activists and/or parents. Activists and parents could potentially be considered as alternative but trustworthy sources of information enabling them to disseminate misinformation about vaccinations.

中文翻译：

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Twitter上的视觉疫苗辩论：社交网络分析

赞成和反对疫苗的使用者使用社交媒体渠道（例如Twitter）加入有关疫苗的对话，传播有关免疫接种的信息或错误信息，并倡导赞成或反对接种疫苗。这些用户不仅共享文本内容，还共享图像以强调他们的消息并影响听众。尽管先前的研究调查了疫苗图像的内容，但很少有人研究这些视觉效果在数字环境中的分布方式。因此，本研究探索了如何在Twitter上共享与疫苗接种相关的图像，以深入了解围绕其传播形成的社区和网络。此外，这项研究还调查了谁会影响疫苗图像的分布，并可能成为疫苗接种信息的潜在看门人。我们对推文样本进行了社交网络分析，并在2016年6月，9月和10月收集了图像。在每个数据集中，疫苗接种前和疫苗接种用户形成了两个相互之间几乎不相互作用的极化网络，并且在其成员之间以不同的方式传播了图像。接种疫苗的用户经常互相转推，加强他们之间的关系，使信息在其社区内变得多余，并确认了他们对接种疫苗的信念。相反，亲疫苗的用户形成了一个分散的网络，具有松散但战略性的连接，从而促进了联网和新疫苗信息的分发。此外，虽然亲疫苗的看门人是非政府组织或卫生专业人员，但是反疫苗的看门人是激进主义者和/或父母。