Department of Public Policy, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States of America.
Department of Health Sciences, Wilfrid Laurier University, Waterloo, ON, Canada.
PLoS One. 2019 Feb 14;14(2):e0212049. doi: 10.1371/journal.pone.0212049. eCollection 2019.
Countries deliver vaccines either through routine health services or supplementary immunization activities (SIAs), usually community-based or door-to-door immunization campaigns. While SIAs have been successful at increasing coverage of vaccines in low- and middle-income countries, they may disrupt the delivery of routine health services. We examine the impact of SIAs on routine vaccine coverage in five low-income countries.
Data on the number and timing of SIAs conducted in various countries was compiled by WHO and obtained through UNICEF. Information on the coverage of vaccines not targeted by SIAs (e.g., DPT) was extracted from the Demographic and Health Surveys. We focus on SIAs that took place between 1996 and 2013 in Bangladesh, Senegal, Togo, Gambia, and Cote d'Ivoire, and examine outcomes for children aged 12-59 months. To avoid biases resulting from non-random placement and timing of SIAs, we use age of a child at her first SIA as an instrumental variable for total exposure to SIAs.
We find that SIA exposure reduced the likelihood of receiving routine vaccines in all the countries included in the study; the coefficients of interest are however statistically insignificant for Gambia and Cote d'Ivoire. In countries that witnessed statistically significant SIA-induced declines in the likelihood of obtaining DPT 3, measles as well as BCG, reductions ranged from 1.3 percentage points (Senegal) to 5.5 percentage points (Bangladesh).
SIA exposure reduced routine vaccination rates in study countries. Efforts should be made to limit the detrimental impact of SIAs on the services provided by routine health systems.
各国通过常规卫生服务或补充免疫活动（SIAs）来提供疫苗，通常是基于社区或挨家挨户的免疫运动。虽然 SIAs 成功地提高了低收入和中等收入国家疫苗的覆盖率，但它们可能会干扰常规卫生服务的提供。我们研究了 SIAs 对五个低收入国家常规疫苗覆盖率的影响。
WHO 汇编了各国开展的 SIA 的数量和时间的数据，并通过 UNICEF 获得。未针对 SIA 进行免疫的疫苗（例如 DPT）的覆盖率信息是从人口与健康调查中提取的。我们专注于 1996 年至 2013 年期间在孟加拉国、塞内加尔、多哥、冈比亚和科特迪瓦进行的 SIA，并研究了 12-59 个月儿童的结果。为了避免由于 SIA 的非随机放置和时间而导致的偏差，我们使用儿童第一次接受 SIA 的年龄作为接受 SIA 总暴露的工具变量。
我们发现，在所有纳入研究的国家中，SIA 暴露降低了接受常规疫苗的可能性；然而，冈比亚和科特迪瓦的结果在统计学上并不显著。在 SIA 导致 DPT3、麻疹和卡介苗接种可能性下降的国家，降幅从塞内加尔的 1.3 个百分点到孟加拉国的 5.5 个百分点不等。
SIA 暴露降低了研究国家的常规疫苗接种率。应努力限制 SIAs 对常规卫生系统提供的服务的不利影响。
