OBJECTIVE To estimate the time-dependent measles effective reproduction number (Rt) as an indicator of the impact of three outbreak response vaccination (ORV) campaigns on measles transmission during a nationwide outbreak in Guinea. METHODS Rt represents the average number of secondary cases generated by a single primary case in a partially immune population during a given time period. Measles Rt was estimated using daily incidence data for 3952 outbreak-associated measles cases in Guinea in 2017 for the time periods prior to, between, and following each of three ORV campaigns using a simple and extensible mathematical model. RESULTS Rt was estimated to be above the threshold value of 1 during the initial growth period of the outbreak until the first ORV campaign began on March 13 (Rt = 1.60, 95% CI: 1.55-1.67). It subsequently dropped below 1 and remained <1 through the end of the year (range: 0.71-0.91), although low levels of transmission persisted. CONCLUSIONS Reduction in Rt coincided with implementation of the ORV campaigns, indicating success of the campaigns at maintaining measles transmission intensity below epidemic growth levels. However, persistent measles transmission remains an issue in Guinea due to insufficient levels of herd immunity. Estimation of Rt should be further leveraged to help decision makers and field staff understand outbreak progress and the timing and type of vaccination efforts needed to halt transmission.

中文翻译：

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2017年几内亚爆发期间，大规模疫苗接种运动对麻疹传播的影响。

目的评估随时间变化的麻疹有效繁殖数（Rt），作为几内亚全国性暴发期间三次暴发应对疫苗接种（ORV）运动对麻疹传播影响的指标。方法Rt代表在给定时间段内部分免疫人群中单个原发病例产生的平均继发病例数。使用简单且可扩展的数学模型，通过使用3个ORV活动中的每一个之前，之间和之后的时间段，使用2017年几内亚3952暴发麻疹病例的每日发病率数据估算了麻疹Rt。结果在暴发的初始生长阶段，直到3月13日第一次ORV运动开始之前，Rt估计都高于阈值1（Rt = 1.60，95％CI：1.55-1.67）。随后，尽管传播水平仍然较低，但到年底仍降至1以下（范围：0.71-0.91）。结论Rt的降低与ORV运动的实施相吻合，表明运动成功地将麻疹的传播强度维持在流行水平以下。然而，由于畜群免疫水平不足，持续的麻疹传播在几内亚仍然是一个问题。应该进一步利用Rt的估算来帮助决策者和现场工作人员了解暴发的进展以及停止传播所需的疫苗接种工作的时间和类型。表明运动成功地将麻疹的传播强度保持在流行水平以下。然而，由于畜群免疫水平不足，持续的麻疹传播在几内亚仍然是一个问题。应进一步利用Rt的估算来帮助决策者和现场工作人员了解暴发的进展以及停止传播所需的疫苗接种工作的时间和类型。表明运动成功地将麻疹的传播强度保持在流行水平以下。然而，由于畜群免疫水平不足，持续的麻疹传播在几内亚仍然是一个问题。应该进一步利用Rt的估算来帮助决策者和现场工作人员了解暴发的进展以及停止传播所需的疫苗接种工作的时间和类型。