Abstract：
In the context of polio eradication efforts, accurate assessment of vaccination programme effectiveness is essential to public health planning and decision making. Such assessments are often based on zero-dose children, estimated using the number of children who did not receive the first dose of the Diphtheria-Tetanus-Pertussis containing vaccine as a proxy. Our study introduces a novel approach to directly estimate the number of children susceptible to poliovirus type 2 (PV2) and uses this approach to provide district-level estimates for South Africa of susceptible children born between 2017 and 2022. We used district-level data on annual doses of inactivated poliovirus vaccine (IPV) administered, live births, and population sizes, from 2017 through 2022. We imputed missing vaccination data, implemented flexible assumptions regarding dose distribution in the eligible population, and used estimated efficacy values for one, two, three, and four doses of IPV, to compute the number of susceptible and immune children by birth year. We validated our approach by comparing an intermediary output with zero-dose children (ZDC) estimated using data reported by WHO/UNICEF Estimates of National Immunization Coverage (WUENIC). Our results indicate high heterogeneity in susceptibility to PV2 across South Africa\'s 52 districts as of the end of 2022. In children under 5 years, PV2 susceptibility ranged from approximately 30 % in districts including Xhariep (31.9 %), Ekurhuleni (30.1 %), and Central Karoo (29.8 %), to less than 4 % in Sarah Baartman (1.9 %), Buffalo City (2.1 %), and eThekwini (3.2 %). Our susceptibility estimates were consistently higher than ZDC over the timeframe. We estimated that ZDC decreased nationally from 155,168 (152,737-158,523) in 2017 to 108,593 in 2021, and increased to 127,102 in 2022, a trend consistent with ZDC derived from data reported by WUENIC. While our approach provides a more comprehensive profile of PV2 susceptibility, our susceptibility and ZDC estimates generally agree in the ranking of districts according to risk.
摘要：
在消除小儿麻痹症的努力中，准确评估疫苗接种计划的有效性对于公共卫生规划和决策至关重要。这种评估通常基于零剂量儿童，使用未接受第一剂含白喉-破伤风-百日咳疫苗的儿童数量作为替代进行估计。我们的研究引入了一种新的方法来直接估计2型脊髓灰质炎病毒（PV2）易感儿童的数量，并使用这种方法为2017年至2022年之间出生的南非易感儿童提供地区一级的估计。我们使用了地区一级的数据，说明脊髓灰质炎灭活疫苗（IPV）的年度剂量，活产,和人口规模，从2017年到2022年。我们估算了丢失的疫苗接种数据，实施了关于合格人群剂量分布的灵活假设，并使用其中一个的估计功效值，两个,三,和四种剂量的IPV，按出生年份计算易感和免疫儿童的数量。我们通过将中间输出与使用WHO/UNICEF国家免疫覆盖率估算（WUENIC）报告的数据估算的零剂量儿童（ZDC）进行比较来验证我们的方法。我们的结果表明，截至2022年底，南非52个地区对PV2的易感性存在高度异质性。在5岁以下的儿童中，PV2敏感性在包括Xhariep在内的地区约为30％（31.9％），Ekurhuleni（30.1%），和中央卡鲁(29.8%)，莎拉·巴特曼(1.9%)不到4%，布法罗市（2.1%），和eThekwini（3.2%）。在这段时间内，我们的易感性估计值始终高于ZDC。我们估计，全国ZDC从2017年的155,168（152,737-158,523）下降到2021年的108,593，并在2022年增加到127,102，这一趋势与WUENIC报告的数据得出的ZDC一致。虽然我们的方法提供了更全面的PV2易感性，我们的易感性和ZDC估计在根据风险对地区进行排名时基本一致.
