Flasche Stefan, Ojal John, Le Polain de Waroux Olivier, Otiende Mark, O'Brien Katherine L, Kiti Moses, Nokes D James, Edmunds W John, Scott J Anthony G
Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, Keppel Street, WC1E 7HT, London, UK.
Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.
BMC Med. 2017 Jun 7;15(1):113. doi: 10.1186/s12916-017-0882-9.
The World Health Organisation recommends the use of catch-up campaigns as part of the introduction of pneumococcal conjugate vaccines (PCVs) to accelerate herd protection and hence PCV impact. The value of a catch-up campaign is a trade-off between the costs of vaccinating additional age groups and the benefit of additional direct and indirect protection. There is a paucity of observational data, particularly from low- and middle-income countries, to quantify the optimal breadth of such catch-up campaigns.
In Kilifi, Kenya, PCV10 was introduced in 2011 using the three-dose Expanded Programme on Immunisation infant schedule and a catch-up campaign in children <5 years old. We fitted a transmission dynamic model to detailed local data, including nasopharyngeal carriage and invasive pneumococcal disease (IPD), to infer the marginal impact of the PCV catch-up campaign over hypothetical routine cohort vaccination in that setting and to estimate the likely impact of alternative campaigns and their dose efficiency.
We estimated that, within 10 years of introduction, the catch-up campaign among children <5 years old prevents an additional 65 (48-84) IPD cases across age groups, compared to PCV cohort introduction alone. Vaccination without any catch-up campaign prevented 155 (121-193) IPD cases and used 1321 (1058-1698) PCV doses per IPD case prevented. In the years after implementation, the PCV programme gradually accrues herd protection, and hence its dose efficiency increases: 10 years after the start of cohort vaccination alone the programme used 910 (732-1184) doses per IPD case averted. We estimated that a two-dose catch-up among children <1 year old uses an additional 910 (732-1184) doses per additional IPD case averted. Furthermore, by extending a single-dose catch-up campaign to children aged 1 to <2 years and subsequently to those aged 2 to <5 years, the campaign uses an additional 412 (296-606) and 543 (403-763) doses per additional IPD case averted. These results were not sensitive to vaccine coverage, serotype competition, the duration of vaccine protection or the relative protection of infants.
We find that catch-up campaigns are a highly dose-efficient way to accelerate population protection against pneumococcal disease.
世界卫生组织建议开展强化免疫活动，作为引入肺炎球菌结合疫苗（PCV）的一部分，以加速群体保护，从而增强PCV的影响。强化免疫活动的价值在于在为更多年龄组接种疫苗的成本与额外直接和间接保护的益处之间进行权衡。目前缺乏观察数据，尤其是来自低收入和中等收入国家的数据，难以量化此类强化免疫活动的最佳广度。
在肯尼亚的基利菲，2011年引入了PCV10，采用三剂次的扩大免疫规划婴儿接种程序，并对5岁以下儿童开展了强化免疫活动。我们将一个传播动力学模型应用于详细的当地数据，包括鼻咽部携带情况和侵袭性肺炎球菌病（IPD），以推断PCV强化免疫活动相对于该环境下假设的常规队列接种的边际影响，并估计替代活动的可能影响及其剂量效率。
我们估计，在引入疫苗后的10年内，与仅引入PCV队列相比，5岁以下儿童的强化免疫活动可在各年龄组预防额外65例（48 - 84例）IPD病例。不开展任何强化免疫活动的接种预防了155例（121 - 193例）IPD病例，每预防1例IPD病例使用1321剂（1058 - 1698剂）PCV。在实施后的几年里，PCV计划逐渐积累群体保护，因此其剂量效率提高：仅开始队列接种10年后，该计划每预防1例IPD病例使用910剂（732 - 1184剂）。我们估计，对1岁以下儿童进行两剂次强化免疫，每额外预防1例IPD病例需额外使用910剂（732 - 1184剂）。此外，将单剂次强化免疫活动扩展至1至2岁儿童，随后扩展至2至5岁儿童，每额外预防1例IPD病例，该活动需额外使用412剂（296 - 606剂）和543剂（403 - 763剂）。这些结果对疫苗覆盖率、血清型竞争、疫苗保护持续时间或婴儿的相对保护不敏感。
我们发现强化免疫活动是加速人群预防肺炎球菌疾病保护的一种高效剂量方式。
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