Hershey Medical School, The Pennsylvania State University, Hershey, PA, USA.
Department of Biology, The Pennsylvania State University, University Park, PA, USA.
BMC Public Health. 2018 Jun 15;18(1):741. doi: 10.1186/s12889-018-5628-x.
Despite progress towards increasing global vaccination coverage, measles continues to be one of the leading, preventable causes of death among children worldwide. Whether and how to target sub-national areas for vaccination campaigns continues to remain a question. We analyzed three metrics for prioritizing target areas: vaccination coverage, susceptible birth cohort, and the effective reproductive ratio (R) in the context of the 2010 measles epidemic in Malawi.
Using case-based surveillance data from the 2010 measles outbreak in Malawi, we estimated vaccination coverage from the proportion of cases reporting with a history of prior vaccination at the district and health facility catchment scale. Health facility catchments were defined as the set of locations closer to a given health facility than to any other. We combined these estimates with regional birth rates to estimate the size of the annual susceptible birth cohort. We also estimated the effective reproductive ratio, R, at the health facility polygon scale based on the observed rate of exponential increase of the epidemic. We combined these estimates to identify spatial regions that would be of high priority for supplemental vaccination activities.
The estimated vaccination coverage across all districts was 84%, but ranged from 61 to 99%. We found that 8 districts and 354 health facility catchments had estimated vaccination coverage below 80%. Areas that had highest birth cohort size were frequently large urban centers that had high vaccination coverage. The estimated R ranged between 1 and 2.56. The ranking of districts and health facility catchments as priority areas varied depending on the measure used.
Each metric for prioritization may result in discrete target areas for vaccination campaigns; thus, there are tradeoffs to choosing one metric over another. However, in some cases, certain areas may be prioritized by all three metrics. These areas should be treated with particular concern. Furthermore, the spatial scale at which each metric is calculated impacts the resulting prioritization and should also be considered when prioritizing areas for vaccination campaigns. These methods may be used to allocate effort for prophylactic campaigns or to prioritize response for outbreak response vaccination.
尽管在提高全球疫苗接种覆盖率方面取得了进展，但麻疹仍然是全球儿童可预防死亡的主要原因之一。是否以及如何针对国家以下各级地区开展疫苗接种运动，仍然是一个悬而未决的问题。我们分析了用于确定目标地区优先顺序的三个指标：疫苗接种覆盖率、易感出生队列和 2010 年马拉维麻疹流行期间的有效繁殖率（R）。
利用 2010 年马拉维麻疹暴发的基于病例的监测数据，我们根据地区和卫生机构集水区的病例报告中既往接种史的比例，估算了疫苗接种覆盖率。卫生机构集水区被定义为距离给定卫生机构比其他任何地方都更近的一组地点。我们将这些估计值与区域出生率相结合，估算每年易感出生队列的规模。我们还根据疫情呈指数增长的观察到的速度，在卫生机构多边形尺度上估算了有效繁殖率（R）。我们将这些估计值结合起来，确定了需要进行补充疫苗接种活动的高优先区域。
所有地区的估计疫苗接种覆盖率为 84%，但范围在 61%至 99%之间。我们发现，有 8 个地区和 354 个卫生机构集水区的估计疫苗接种覆盖率低于 80%。出生队列规模最大的地区通常是拥有高疫苗接种覆盖率的大型城市中心。估计的 R 值在 1 到 2.56 之间。作为优先地区的地区和卫生机构集水区的排名因所使用的指标而异。
每种优先排序指标都可能导致离散的疫苗接种运动目标地区；因此，在选择一种指标而不是另一种指标时存在权衡。然而，在某些情况下，某些地区可能会被所有三个指标同时列为优先地区。这些地区应特别关注。此外，用于计算每个指标的空间尺度会影响最终的优先排序，在为疫苗接种运动确定优先地区时也应考虑这一点。这些方法可用于分配预防性运动的工作，或为疫情应对疫苗接种提供优先响应。
