Zeroing in on zero-dose
Challenges and opportunities for improving equity and coverage among zero-dose and under-immunised children in four countries.
- 14 February 2024
- 5 min read
- by the Zero-Dose Learning Hub
Identifying and reaching zero-dose (ZD) children remains one of the most complex challenges in the pursuit of global immunisation equity. But how can we reach ZD and under-immunised children without knowing who they are and where they live?
The Zero-Dose Learning Hub (ZDLH), funded by Gavi, represents the Alliance's investment in reaching ZD children by turning high-quality data and evidence into actionable strategies to support country learning hubs to implement Gavi's identification, reach, monitoring, measurement and advocacy (IRMMA) framework. The ZDLH model features a network of national organisations working in four countries, including Bangladesh, Mali, Nigeria and Uganda.
As the four Country Learning Hubs (CLHs) began their work, the Learning Hub's global consortium, led by JSI Research & Training Institute, Inc., scanned the current immunisation landscape in each country to better understand the immunisation context. Through literature reviews and secondary data analysis, the Learning Hub identified critical gaps, challenges, and opportunities to improve the identification, reach, monitoring, management and advocacy for zero-dose and under-immunised children.
The Zero-Dose Learning Hub will work hand-in-hand with the country hubs on the sharing and uptake of evidence and learning around specific interventions to identify and reach zero-dose and under-immunised children.
The resulting landscape analyses identified factors affecting the immunisation system within the four Learning Hub countries, including immunisation coverage equity, human resources, immunisation policies and financing, environmental context and community health structures.
Developing a deeper understanding of these factors and regional contexts can be used to create more targeted, contextually-appropriate immunisation programming. The findings from the landscape analyses, summarised below, provide opportunities for others working to reach ZD and under-immunised children to apply lessons learned and strengthen their own data collection and implementation approaches.
Key cross-country findings
While each of the four Country Learning Hub countries have a unique immunisation context, several cross-country findings emerged:
1. Estimates of the number of zero-dose children vary due to discrepancies in population estimates and pentavalent vaccine coverage.
Pentavalent, a vaccine against five major diseases, serves as a proxy indicator for zero-dose children. It is used as a proxy for access to routine immunisation services because it is typically administered during infant visits at 6, 10 and 14 weeks.
If a child has received the Penta1 vaccine, they are not classified by the Alliance as zero-dose. Discrepancies in population estimates, a common challenge across the four Learning Hub countries, make it difficult to calculate coverage rates and determine the true scope of the problem of zero-dose and under-immunised children. The landscapes in the four countries compared zero-dose estimates from the WHO/UNICEF Estimates of National Immunization Coverage (WUENIC) and Institute for Health Metrics and Evaluation (IHME). The difference in calculation methodology can result in estimates that vary by more than 100,000 children (Table 1). Given the wide variation in numbers, these relatively imprecise estimates serve primarily as a guide for broader implementation planning purposes.
Table 1: Estimates of the Number of ZD Children
2. Using data from the Demographic and Health Surveys (DHS), the Zero-Dose Learning Hub found that certain sociodemographic variables are more important predictors of zero-dose status in some Learning Hub countries than others. These include birth order, mother's education, wealth quintile, geographic region, and ethnic group.
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For example, while residing in a rural location is a strong predictor of zero-dose status in Mali and Nigeria, this is not the case in Bangladesh or Uganda, where the prevalence of ZD children is similar in rural and urban areas (Figure 1). IHME data from 2021 shows regional variations in immunisation rates (Figure 2). While national DHS data may point to certain sociodemographic factors as predicting ZD status, their importance may vary subnationally, highlighting the importance of adapting research and programming efforts to specific contexts. Utilising both sources of data in tandem can allow funders and programme teams to better inform future efforts.
Figure 1: Sociodemographic Predictors of ZD Status Vary Widely Across Each of the Four Countries
3. Partnerships are fundamental to the immunisation systems in all countries.
In all four Country Learning Hub countries, a variety of partners contribute to government engagement, funding, research, implementation and technical assistance. These partnerships will be important for the hubs to engage and coordinate with in order to reach zero-dose and under-immunised children.
Figure 2: Number of ZD Children by District
4. The landscape analyses also provided insight into two key research gaps:
a) Quality of immunisation data: there are very few existing assessments looking into the quality (completeness, timeliness, accuracy) of immunisation data at the service delivery level. Additionally, data on the human resources needed to support the immunisation system is limited, raising questions about staffing challenges in remote areas. Some of these questions include whether there is enough staff to support immunisation and what are the challenges that the immunisation workforce faces.
b) Immunisation coverage rates across contexts: the Zero-Dose Learning Hub found few research studies assessing immunisation coverage across different environmental and sociodemographic contexts, including among ethnic minorities, refugees, people in hard-to-reach and remote areas, urban slums, conflict-affected areas, and conflict and climate-change affected areas. Understanding immunisation coverage in these contexts, as well as the barriers to immunisation, is essential for achieving equitable immunisation coverage.
Addressing research gaps and future interventions
Moving forward, the Zero-Dose Learning Hub will work hand-in-hand with the country hubs on the sharing and uptake of evidence and learning around specific interventions to identify and reach zero-dose and under-immunised children. Limited evidence on the quality of lower-level administrative immunisation data highlights the importance of robust data collection and analysis of the quality of existing administrative data systems.
In addition, the observed lack of research studies on immunisation coverage across diverse contexts provides funders and other programmes the opportunity to implement context-specific research studies that bridge the knowledge gap and improve targeted implementation efforts.
The ZDLH landscape analyses highlight the complexities of childhood immunisation in each of the four countries and provide a backdrop to the work the country hubs have undertaken to address local challenges to improving immunisation coverage. These findings emphasise the need for high quality, local and contextualised immunisation data to promote immunisation equity. Together, immunisation stakeholders can make a collective commitment to addressing the research gaps to achieve the goal of universal and equitable immunisation coverage.
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