Childhood immunization is one of the most effective health interventions, making it a key indicator of progress towards universal health coverage. In the last decade, improvements in coverage have been made globally, however, slow progress has been documented in sub-Saharan Africa with considerable subnational variations. We explore potential drivers of equitable immunization services based on subnational DTP3 coverage estimates.

Using vaccine coverage at the 5 by 5 km area from 2000 to 2016, we quantify inequality using three measures. We assess the shortfall inequality which is the average deviation across subnational units from that with the highest coverage for each country. Secondly we estimate the threshold index, the proportion of children below a globally set subnational coverage target, and lastly, a Gini coefficient representing the within-country distribution of coverage. We use time series analyses to quantify associations with immunization expenditures controlling for country socio-economic and population characteristics.

Development assistance, maternal education and governance were associated with reductions in inequality. Furthermore, high quality governance was associated with a stronger relationship between development assistance and reductions in inequality. Results from this analysis also indicate that countries with the lowest coverage suffer the highest inequalities. We highlight growing inequalities among countries which have met national coverage targets such as South Africa and Kenya. In 2016, values for the shortfall inequality ranged from 1% to 43%, the threshold index from 0% to 100% and Gini coefficient from 0.01 to 0.37. Burundi, Comoros, Eswatini, Lesotho, Namibia, Rwanda, and Sao Tome and Principe had the least shortfall inequality (<5%) while Angola, Ethiopia and Nigeria had values greater than 40%. A similar picture was noted for the other dimensions of inequality among these particular countries.

Immunization program investments offer promise in addressing inequality, however, domestic mechanisms for resource implementation and accountability should be strengthened to maximize gains in coverage.

儿童免疫是最有效的健康干预措施之一，使其成为实现全民健康覆盖的关键指标。在过去的十年中，全球范围内的覆盖率有所提高，但是，在撒哈拉以南非洲地区，据记录进展缓慢，地方差异很大。我们根据国家以下DTP3覆盖率估算值来探索公平免疫服务的潜在驱动因素。

利用2000年至2016年在5 x 5公里范围内的疫苗覆盖率，我们使用三种方法对不平等现象进行量化。我们评估了不足的不平等，这是地方政府部门与每个国家/地区覆盖率最高的地方之间的平均偏差。其次，我们估计阈值指数，低于全球设定的国家以下覆盖率目标的儿童比例，最后是代表国内覆盖率分布的基尼系数。我们使用时间序列分析来量化与控制国家社会经济和人口特征的免疫接种支出的关联。

发展援助，孕产妇教育和治理与不平等现象的减少有关。此外，高质量的治理与发展援助与减少不平等之间更牢固的关系有关。该分析的结果还表明，覆盖率最低的国家遭受的不平等程度最高。我们着重指出，在达到国家覆盖率目标的国家（如南非和肯尼亚）之间，不平等现象日益严重。2016年，短缺不平等的值从1％到43％，阈值指数从0％到100％，基尼系数从0.01到0.37。布隆迪，科摩罗，埃斯瓦蒂尼，莱索托，纳米比亚，卢旺达和圣多美和普林西比的缺口不平等最少（<5％），而安哥拉，埃塞俄比亚和尼日利亚的贫富差距均大于40％。

免疫方案投资为解决不平等现象提供了希望，但是，应加强国内资源实施和问责机制，以最大程度地扩大覆盖面。