Background

Substantial outbreaks of yellow fever in Angola and Brazil in the past 2 years, combined with global shortages in vaccine stockpiles, highlight a pressing need to assess present control strategies. The aims of this study were to estimate global yellow fever vaccination coverage from 1970 through to 2016 at high spatial resolution and to calculate the number of individuals still requiring vaccination to reach population coverage thresholds for outbreak prevention.

Methods

For this adjusted retrospective analysis, we compiled data from a range of sources (eg, WHO reports and health-service-provider registeries) reporting on yellow fever vaccination activities between May 1, 1939, and Oct 29, 2016. To account for uncertainty in how vaccine campaigns were targeted, we calculated three population coverage values to encompass alternative scenarios. We combined these data with demographic information and tracked vaccination coverage through time to estimate the proportion of the population who had ever received a yellow fever vaccine for each second level administrative division across countries at risk of yellow fever virus transmission from 1970 to 2016.

Findings

Overall, substantial increases in vaccine coverage have occurred since 1970, but notable gaps still exist in contemporary coverage within yellow fever risk zones. We estimate that between 393·7 million and 472·9 million people still require vaccination in areas at risk of yellow fever virus transmission to achieve the 80% population coverage threshold recommended by WHO; this represents between 43% and 52% of the population within yellow fever risk zones, compared with between 66% and 76% of the population who would have required vaccination in 1970.

Interpretation

Our results highlight important gaps in yellow fever vaccination coverage, can contribute to improved quantification of outbreak risk, and help to guide planning of future vaccination efforts and emergency stockpiling.

Funding

The Rhodes Trust, Bill & Melinda Gates Foundation, the Wellcome Trust, the National Library of Medicine of the National Institutes of Health, the European Union's Horizon 2020 research and innovation programme.

中文翻译：

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1970年至2016年全球黄热病疫苗接种覆盖率：调整后的回顾性分析

背景

在过去的两年中，安哥拉和巴西的黄热病大量爆发，再加上全球疫苗库存的短缺，凸显了评估当前控制策略的迫切需求。这项研究的目的是以高空间分辨率估算1970年至2016年的全球黄热病疫苗接种覆盖率，并计算仍需要接种疫苗才能达到预防暴发的人口覆盖阈值的人数。

方法

对于此调整后的回顾性分析，我们收集了来自1939年5月1日至2016年10月29日之间黄热病疫苗接种活动的各种数据来源（例如，WHO报告和卫生服务提供方注册处）。如何针对疫苗运动进行针对性，我们计算了三个人口覆盖率值以涵盖其他方案。我们将这些数据与人口统计信息相结合，并随时间跟踪疫苗接种的覆盖率，以估算从1970年至2016年间存在黄热病病毒传播风险的国家中，每二级行政区划曾接受黄热病疫苗接种的人口比例。

发现

总体而言，自1970年以来，疫苗的覆盖率已经出现了实质性的增长，但是当代黄热病危险区的覆盖率仍然存在明显差距。我们估计，在有黄热病病毒传播危险的地区，仍有393·700万人至472·900万人需要接种疫苗，以达到WHO所建议的80％的人口覆盖率门槛；占黄热病危险区人口的43％至52％，而1970年需要接种疫苗的人口则为66％至76％。

解释

我们的结果突显了黄热病疫苗接种覆盖率方面的重要差距，可以有助于改进对爆发风险的量化，并有助于指导未来疫苗接种工作和应急储备的规划。

资金

罗德基金会，比尔和梅琳达·盖茨基金会，惠康基金会，国立卫生研究院国家医学图书馆，欧盟的Horizo​​n 2020研究与创新计划。