The Vaccination Act of 1853, which mandated smallpox vaccination for infants in England, prompted the emergence of the Anti-Vaccination League, widespread street protests, and the appearance of several anti-vaccination journals. Various criticisms were levelled: that vaccines were unsafe; that vaccinations were “unchristian”; that the mandate was a violation of personal liberties. Conspiracy theories and misinformation abounded.

When we reflect on vaccine hesitancy in the COVID-19 era, it is worth remembering that these sentiments are not new. What is relatively new is the systematic empirical exploration of the psychological mechanisms underpinning vaccine refusal: examination of Web of Science data suggests that 35% of the papers ever written on the psychology of vaccines were published since 2020. Also new are concerns that vaccine refusal presents a mental health challenge. Since the emergence of the pandemic and associated debates about mandating vaccination, there has been concern that vaccine hesitant people are being caught in a self-reinforcing cycle of mistrust, stigma, isolation, and psychological distress. Parallel to this, emerging data show that those with pre-existing mental disorders are disproportionately likely to die from COVID-19¹. In this context, mental health professionals are asking: why would people refuse COVID-19 vaccination, and what can be done about it? Here I explore three factors implicated in vaccine refusal – flawed risk appraisal, conspiracy theorizing, and ideology – and reflect on their implications for informing communication strategies.

A curious aspect of the human mind is that we struggle to rationally appraise risk. Arguments such as “you have a one in a million chance of developing lethal blood clots if you take this vaccine” or “the risks of vaccinating are far lower than the risks of not vaccinating” require us to think analytically and dispassionately about risk. But our evolutionary history did not prepare us for a world of science, statistics and base rates. Rather, our minds are designed to appraise risk as a function of vivid events and narratives, processed emotionally². Base rate statistics have surprisingly little impact in the face of dramatic “case rate” stories of otherwise healthy people whose lives have been ruined or lost because of adverse reactions to vaccines. These images and narratives are a stock strategy of the anti-vaccination movement, but also a common feature of mainstream news coverage of COVID-19 vaccines. In this context, it would be human nature to experience anxiety at the thought of taking COVID-19 vaccination, particularly among those of us who are predisposed to intuitive or experiential cognitive styles.

Overlaid on this basic tendency, it is possible that clinical or subclinical issues can complicate people’s ability to objectively appraise risk. It has been speculated that certain mental health conditions – for example, blood-injection-injury phobia – might predispose people to feeling instinctive aversion to vaccinations³. Related to this, a large-scale survey found that participants’ levels of disgust or repugnance at the sight of anaesthetic needles or blood was predictive of vaccine hesitancy across 25 nations, much more so than their levels of education⁴.

Attempts to reassure the population that vaccines are safe are further complicated when people dispute the validity of scientific messaging. For some, scientists, governments and drug developers are part of a cabal of vested interests who exaggerate evidence that vaccines are helpful and cover up evidence that vaccines can be harmful. One of the most powerful predictors of vaccine hesitancy is the conspiracist worldview: the notion that it is commonplace for groups of elites to conduct elaborate hoaxes on the public in near-perfect secrecy. Particularly in the West, a surprisingly large amount of variance in vaccine hesitancy can be accounted for by merely knowing whether people think that Princess Diana was murdered, or that 9/11 was an inside job⁴. When people have this worldview, messages that would normally be persuasive – for example, government assurances of safety and scientific consensus around effectiveness – can be inverted to be proof of a conspiracy. Unable to trust official messaging, these people may place implicit faith in messengers that mirror their distrust, such as elements of the wellness industry and some populist politicians⁵.

It should be noted that there may be some sensible foundation to the mistrust, although in this case it is over-generalized to embrace objectively implausible conspiracy theories. It is common sense to argue that we should be vigilant to signs that vested issues have a corrupting influence on health care (the thick layers of independent regulation around vaccine development are testament to the fact that the health system shares that concern). It is also worthwhile remembering that there are traumatic historical examples of medical racism, that are circulated widely within certain communities while they debate the safety of vaccines. For members of society who feel protected by the system, it is easier to communicate that the system can be trusted than for people who feel marginalized by the system, which may be a reason why in some countries culturally and linguistically diverse communities have been the slowest to vaccinate against COVID-19⁶.

Finally, there is a convergence of evidence that ideological fac­­tors have shaped people’s willingness to embrace COVID-19 vaccines. For people who are committed to small government, eco­nomic progress, and individual freedoms (as are many conservatives), the regulatory response to a pandemic can be perceived as ideologically noxious. Faced with an aversive solution to the pandemic, conservatives may be motivated to instead question the COVID-19 science. In some countries such as the US, this ideological divide is one of the most recognizable phenomena of the COVID-19 era: although there are small pockets of vaccination resistance among the far left, conservatives report less intention to vaccinate than liberals overall⁷. Having been drawn into the algorithm that defines one’s political persuasion, the decision to vaccinate has become not just a reflection of what people believe, but also a way of signalling to others one’s political and ideological identities.

Understanding the factors discussed above helps make sense of what, for many scientists and health professionals, is one of the most exasperating and difficult-to-understand features of the vaccination debate: facts are not enough. Merely repeating evidence has been a notoriously ineffective way of shifting attitudes among those who self-identify as anti-vaccination⁸. One reason for this is that people do not always behave like cognitive scientists, weighing up evidence before reaching a conclusion. Frequently, we behave more like cognitive lawyers, selectively exposing ourselves, critiquing, and remembering evidence that reinforces a conclusion that feels “right” for us. Successful communication requires deep listening and an attentiveness to the fears, worldviews and ideologies that might be motivating COVID-19 refusal⁹. Persuasion attempts that are responsive to these underlying “attitude roots” are more likely to be successful than those that sail above them with an exclusive focus on facts and data³.

Finally, mental health professionals recognize as much as any­one the importance of communication that is non-stigmatizing and inclusive. Although the public face of the anti-vaccination movement sometimes seems strident and unworthy of empathy, community members who align with those views are frequently characterized by anxiety and uncertainty. There is the potential for negative feedback loops, where the vaccine hesitant feel misunderstood and stigmatized, reinforcing their worldview that the system is corrupted and lacking in humanity. Feeling socially isolated, vaccine refusers may be driven toward the online communities and misinformation echo chambers that reinforce their fears. Respectful and inclusive communication is not just the “nice” thing to do; on a pragmatic level, it is a pre-requisite for enabling positive change.

1853 年的《疫苗接种法》要求为英格兰的婴儿接种天花疫苗，这促使反疫苗接种联盟的出现、广泛的街头抗议活动以及一些反疫苗接种期刊的出现。提出了各种批评：疫苗不安全；疫苗接种是“非基督教的”；授权是对个人自由的侵犯。阴谋论和错误信息比比皆是。

当我们反思 COVID-19 时代对疫苗的犹豫时，值得记住的是，这些情绪并不新鲜。相对较新的是对支持疫苗拒绝的心理机制的系统实证探索：对 Web of Science 数据的检查表明，自 2020 年以来，有 35% 的关于疫苗心理学的论文发表。疫苗拒绝带来的担忧也是新的心理健康挑战。自从大流行和有关强制接种疫苗的相关辩论出现以来，人们一直担心对疫苗犹豫不决的人正陷入不信任、耻辱、孤立和心理困扰的自我强化循环。与此同时，新出现的数据表明，那些先前存在精神障碍的人死于 COVID-19 的可能性不成比例。¹ . 在这种情况下，心理健康专业人士会问：为什么人们会拒绝接种 COVID-19 疫苗，对此能做些什么？在这里，我探讨了与拒绝接种疫苗有关的三个因素——有缺陷的风险评估、阴谋论和意识形态——并反思它们对告知沟通策略的影响。

人类思维的一个奇怪方面是我们努力理性地评估风险。诸如“如果你服用这种疫苗，你有百万分之一的机会发生致命的血栓”或“接种疫苗的风险远低于不接种疫苗的风险”等论点，我们需要对风险进行分析和冷静地思考。但是我们的进化史并没有让我们为科学、统计和基准利率的世界做好准备。相反，我们的思维被设计为根据生动的事件和叙述来评估风险，并在情感上进行处理². 面对那些原本健康的人因对疫苗的不良反应而被毁或失去生命的戏剧性“病例率”故事，基准率统计数据的影响却出人意料地小。这些图像和叙述是反疫苗运动的股票策略，也是 COVID-19 疫苗主流新闻报道的共同特征。在这种情况下，一想到要接种 COVID-19 疫苗就会感到焦虑是人类的天性，尤其是在我们这些倾向于直觉或体验认知方式的人中。

叠加在这一基本趋势之上，临床或亚临床问题可能会使人们客观评估风险的能力复杂化。据推测，某些心理健康状况——例如，血液注射伤害恐惧症——可能会使人们对接种疫苗产生本能的厌恶³。与此相关，一项大规模调查发现，参与者对麻醉针头或血液的厌恶或厌恶程度可以预测 25 个国家/地区对疫苗的犹豫，远高于他们的教育水平⁴。

当人们对科学信息的有效性提出质疑时，试图向人们保证疫苗是安全的会变得更加复杂。对一些人来说，科学家、政府和药物开发商是既得利益集团的一部分，他们夸大疫苗有用的证据，掩盖疫苗可能有害的证据。对疫苗犹豫不决的最有力预测因素之一是阴谋论世界观：精英团体在近乎完美的秘密下对公众进行精心策划的恶作剧是司空见惯的。尤其是在西方，仅知道人们是否认为戴安娜王妃是被谋杀的，或者 9/11 是内部工作^{4就可以解释疫苗犹豫的巨大差异。}. 当人们拥有这种世界观时，通常具有说服力的信息——例如，政府对安全的保证和围绕有效性的科学共识——可以被颠倒为阴谋的证据。由于无法信任官方信息，这些人可能会隐含信任反映他们不信任的信息，例如健康行业的元素和一些民粹主义政客⁵。

应该指出的是，这种不信任可能有一些合理的基础，尽管在这种情况下，它过于笼统地接受了客观上不可信的阴谋论。认为我们应该警惕既得问题对医疗保健产生腐败影响的迹象是常识（围绕疫苗开发的独立监管层证明了卫生系统也有这种担忧的事实）。还值得记住的是，医学种族主义的创伤性历史例子在某些社区内广泛传播，同时他们辩论疫苗的安全性。对于感觉受到系统保护的社会成员来说，与感觉被系统边缘化的人相比，更容易传达系统可以信任的信息，⁶ .

最后，有一系列证据表明，意识形态因素影响了人们接受 COVID-19 疫苗的意愿。对于致力于小政府、经济进步和个人自由的人（就像许多保守派一样），对大流行的监管反应可以被视为在意识形态上有害。面对对大流行的厌恶解决方案，保守派可能会转而质疑 COVID-19 科学。在美国等一些国家，这种意识形态分歧是 COVID-19 时代最明显的现象之一：尽管极左翼中有一小部分人对疫苗接种有抵抗力，但总体而言，保守派的疫苗接种意愿低于自由派⁷. 被纳入定义一个人的政治说服力的算法之后，接种疫苗的决定不仅反映了人们的信仰，而且还成为向他人传达政治和意识形态身份的一种方式。

了解上面讨论的因素有助于理解对于许多科学家和卫生专业人员来说，疫苗辩论中最令人恼火和难以理解的特征之一是：事实还不够。仅仅重复证据是一种众所周知的无效方式来改变那些自我认定为反疫苗接种的人的态度⁸. 造成这种情况的一个原因是，人们并不总是像认知科学家那样，在得出结论之前权衡证据。通常，我们的行为更像认知律师，选择性地暴露自己、批评和记住证据，这些证据强化了对我们来说“正确”的结论。成功的沟通需要深入倾听并关注可能导致 COVID-19 拒绝的恐惧、世界观和意识形态⁹。对这些潜在的“态度根源”做出反应的说服尝试比那些只关注事实和数据而超越它们的说服尝试更有可能成功³。

最后，精神卫生专业人员和任何人一样认识到非污名化和包容性沟通的重要性。尽管反疫苗运动的公众形象有时看起来很刺耳，不值得同情，但与这些观点一致的社区成员往往以焦虑和不确定为特征。有可能出现负反馈循环，疫苗犹豫不决者会感到被误解和污名化，从而强化了他们的世界观，即该系统已腐败且缺乏人性。感觉社会孤立，疫苗拒绝者可能会被驱赶到在线社区和错误信息回声室，这加剧了他们的恐惧。尊重和包容的沟通不仅仅是“好”的事情。在务实的层面上，这是促成积极变革的先决条件。