Estimates for vaccine uptake models.

During a novel pandemic, significant uncertainty drives individuals to seek expert guidance on preventive measures such as vaccination. Yet, it remains poorly understood how people process information in a highly complex landscape of global health governance where multiple experts may offer competing, repetitive, or contradictory advice. This study investigates the influence of World Health Organization (WHO)’s endorsements of vaccines amidst this environment. In fall 2020, we conducted a randomized conjoint experiment in Canada (832 respondents, 8,320 profiles evaluated), Japan (1,474, 14,740), and the United States (1,001, 10010), focusing on both whether and when people choose to vaccinate against COVID-19. Our experiment randomly varied exposure to vaccine endorsement information from several prominent global health governance players, including the WHO, the Centers for Disease Control and Prevention (CDC), Oxford University, and the Gates Foundation; and, unlike previous studies, different combinations of these endorsements were used. WHO endorsements increase individuals’ willingness to vaccinate more quickly, even when accompanied by endorsements from other credible organizations. However, the effect of WHO endorsements is not significantly stronger than that of other organizations. Notably, the impact of the WHO’s endorsement diminishes as the number of endorsements from other organizations increases. The WHO has the greatest impact when it is the first (or among the first) of many organizations to endorse a vaccine as safe and effective, and it may help inspire public confidence in less effective (but potentially lifesaving) vaccines. Overall, our study shows that WHO endorsements significantly reduce vaccine hesitancy, but endorsements from other global actors can exert comparable effects. This highlights that effective global health communication thus depends not on a single authoritative voice but on the timely coordination of multiple credible actors, underscoring the resilience of the global health system in promoting vaccine acceptance.在新型大流行疫情期间，显著的不确定性促使民众寻求疫苗接种等防疫措施的专业指导。然而，在全球卫生治理高度复杂的语境下，多方专家可能会给出相互竞争、重复或矛盾的建议，民众如何在此类环境中处理相关信息，目前仍鲜有研究阐明。本研究旨在探究在此背景下，世界卫生组织（World Health Organization，WHO）对疫苗的认可所产生的影响。2020年秋季，我们分别在加拿大（832名受访者，评估8320份档案）、日本（1474名受访者，评估14740份档案）与美国（1001名受访者，评估10010份档案）开展了随机联合实验，重点关注民众是否以及何时选择接种新冠疫苗。本实验随机调整了受访者接触的疫苗认可信息来源，涵盖世界卫生组织（WHO）、美国疾病控制与预防中心（Centers for Disease Control and Prevention，CDC）、牛津大学以及盖茨基金会等多家知名全球卫生治理主体；与既往研究不同的是，本实验采用了这些认可信息的不同组合方式。即便同时获得其他可信机构的认可，世界卫生组织的认可仍能更快提升民众的疫苗接种意愿。不过，世界卫生组织认可的影响并未显著强于其他机构。值得注意的是，随着其他机构认可数量的增加，世界卫生组织认可的影响会逐渐减弱。当世界卫生组织成为众多机构中首个（或首批）认可某款疫苗安全有效的主体时，其影响最为显著；同时，该组织的认可还有助于提升民众对有效性较低（但具备潜在救生价值）疫苗的信心。总体而言，本研究表明，世界卫生组织的认可可显著降低疫苗犹豫，但其他全球行为体的认可也能产生相当的效果。这一发现凸显，有效的全球卫生传播并非依赖单一权威声音，而是需要多个可信主体的及时协同，这也彰显了全球卫生体系在提升疫苗接受度方面的韧性。