Published in PLOS One on 2026-09-03, this study is presented as an attributed evidence briefing. The excerpts below are the original researchers’ words, reproduced under their Creative Commons Attribution licence. Health Signal has selected the abstract and, where needed, opening background paragraphs; the complete methods, results, limitations and references remain in the linked paper.
Original study title: Effectiveness of monitoring mechanisms in reducing immunization dropouts among infants in health facilities of Maridi County, South Sudan
Original authors: Daniel Opinile Mark Igga, Nzomo Mwita, Kennedy Muni
Source: PLOS One • DOI 10.1371/journal.pone.0356268
Read the complete primary study ↗ · Creative Commons Attribution licence
From the researchers
Abstract
Childhood immunization is among the most cost-effective public health strategies available, yet dropout rates, the proportion of infants who begin but fail to complete the recommended vaccination schedule, remain a persistent obstacle to achieving high and equitable coverage. Global third-dose pentavalent coverage stood at 86% in 2019, declined to 84% in 2020, and fell further to 82% in 2021, consistently falling short of the 85% minimum target. This shortfall is especially pronounced in fragile health systems such as that of South Sudan, where facility-level and community-level monitoring mechanisms vary widely in availability and quality.
I conducted a prospective cohort study from 1 October to 31 December 2023 in Maridi County, Western Equatoria State, South Sudan. Fourteen health facilities were selected by stratified random sampling (seven from payams with active Boma Health Initiative [BHI] activities and seven from payams without). One vaccinator per facility was selected by coin toss, yielding 26 participants. A semi-structured interview guide administered in month one and a monthly observation checklist applied across all three months were used to collect data. Data were analyzed using descriptive statistics, chi-square tests, Spearman correlations, and multivariable regression to assess associations between monitoring mechanisms and facility-level dropout rates.
Three of the 14 facilities (21%) had no monitoring chart; 28.6% recorded a dropout rate above 10%, while half (50%) achieved the target of below 10%. Facilities with updated monitoring charts were significantly less likely to record high dropout rates (Spearman r = −0.725, p = 0.003). Boma Health Workers (BHWs), community-level health personnel who mobilize, trace, and refer immunization defaulters, were attached to 64% of facilities; 91.7% of facility-months in the low-dropout category had BHWs present, compared with 37.5% in the high-dropout category. Over the three months of observation, the proportion of facilities recording a dropout rate above 10% fell by 9.6 percentage points.
Facility-based monitoring tools used by health workers (monitoring charts, immunization registers, and defaulter tracing systems) and community-based monitoring carried out by BHWs were each independently associated with lower dropout rates, and their combination appears to have a complementary effect. Neither mechanism was sufficient alone. We recommend that health workers use monitoring tools consistently and that the Boma Health Initiative be scaled up to health facilities currently without BHWs.
Introduction
Immunization is one of the most efficient and successful health interventions for the reduction of child morbidity and mortality. The World Health Organization (WHO) established the Expanded Programme on Immunization (EPI) in 1974 to ensure universal access to routinely recommended childhood immunizations [1]. Despite half a century of progress under EPI, a substantial gap persists between the children who begin vaccination and those who complete it, a gap commonly measured as the immunization dropout rate.
Reading this evidence
Use the full paper to check the study design, participant selection, comparator and outcome definitions before drawing a practical conclusion. An association does not by itself show cause and effect. A reported performance measure needs its denominator and uncertainty. A finding from a particular facility, sample or time period should retain that scope when it is discussed elsewhere.
This briefing makes the source accessible within the wider financing & policy desk. It does not assess an individual patient or certify a product. When considering relevance to another health system, examine the original authors’ account of context and limitations, then seek local implementation evidence. The related reporting below provides other studies to read alongside this one; it is a topic connection, rather than a claim that their results are directly comparable.
© 2026 Daniel Opinile Mark Igga, Nzomo Mwita, Kennedy Muni. Excerpts reproduced under CC BY. Selection, formatting and contextual notes by Health Signal. The researchers are the authors of the source study, not members of Health Signal’s staff.
Explore connected evidence
- Evidence brief: Prevalence, spatial patterns and determinants of zero-dose vaccination among children aged 12–23 months in Sub-Saharan Africa: A multilevel spatial analysis
- Evidence brief: Challenges, opportunities and best practices in routine childhood vaccination services delivery in urban slums and pastoralist regions of Ethiopia: An exploratory qualitative study in marginalized settings
- Evidence brief: Sociodemographic and geographic determinants of childhood immunization coverage and equity in Ghana: Analysis of the 2022 demographic and health survey
