Staples J Erin, Barrett Alan D T, Wilder-Smith Annelies, Hombach Joachim
Arboviral Diseases Branch, U.S. Centers for Disease Control and Prevention, Fort Collins, CO USA.
Department of Pathology and Sealy Institute for Vaccine Sciences, University of Texas Medical Branch, Galveston, TX USA.
NPJ Vaccines. 2020 Jul 6;5(1):54. doi: 10.1038/s41541-020-0205-6. eCollection 2020.
Yellow fever (YF) virus is a mosquito-borne flavivirus found in Sub-Saharan Africa and tropical South America. The virus causes YF, a viral hemorrhagic fever, which can be prevented by a live-attenuated vaccine, strain 17D. Despite the vaccine being very successful at decreasing disease risk, YF is considered a re-emerging disease due to the increased numbers of cases in the last 30 years. Until 2014, the vaccine was recommended to be administered with boosters every 10 years, but in 2014 the World Health Organization recommended removal of booster doses for all except special populations. This recommendation has been questioned and there have been reports of waning antibody titers in adults over time and more recently in pediatric populations. Clearly, the potential of waning antibody titers is a very important issue that needs to be carefully evaluated. In this Perspective, we review what is known about the correlate of protection for full-dose YF vaccine, current information on waning antibody titers, and gaps in knowledge. Overall, fundamental questions exist on the durability of protective immunity induced by YF vaccine, but interpretation of studies is complicated by the use of different assays and different cut-offs to measure seroprotective immunity, and differing results among certain endemic versus non-endemic populations. Notwithstanding the above, there are few well-characterized reports of vaccine failures, which one would expect to observe potentially more with the re-emergence of a severe disease. Overall, there is a need to improve YF disease surveillance, increase primary vaccination coverage rates in at-risk populations, and expand our understanding of the mechanism of protection of YF vaccine.
黄热病（YF）病毒是一种通过蚊子传播的黄病毒，在撒哈拉以南非洲和南美洲热带地区均有发现。该病毒会引发黄热病，一种病毒性出血热，可通过减毒活疫苗17D株预防。尽管该疫苗在降低疾病风险方面非常成功，但由于过去30年病例数增加，黄热病被视为一种再度出现的疾病。直到2014年，该疫苗建议每10年进行加强接种，但在2014年世界卫生组织建议除特殊人群外，取消所有人群的加强剂量。这一建议受到质疑，并且有报告称，随着时间推移，成人抗体滴度下降，最近儿童群体中也出现了这种情况。显然，抗体滴度下降的可能性是一个非常重要的问题，需要仔细评估。在这篇观点文章中，我们回顾了关于全剂量黄热病疫苗保护相关性的已知信息、当前关于抗体滴度下降的信息以及知识空白。总体而言，黄热病疫苗诱导的保护性免疫的持久性存在一些基本问题，但由于使用不同的检测方法和不同的临界值来衡量血清保护性免疫，以及某些地方性与非地方性人群之间结果不同，研究的解读变得复杂。尽管如此，疫苗失败的特征明确的报告很少，而对于一种严重疾病的再度出现，人们可能会预期观察到更多疫苗失败的情况。总体而言，有必要改善黄热病疾病监测状况，提高高危人群的初次疫苗接种覆盖率，并扩大我们对黄热病疫苗保护机制的理解。
