Estimating the cost of reaching zero-dose children through outreach in Nigeria

 Nigeria has the largest population of zero-dose (ZD) children globally—an estimated 2.1 million in 2023—with prevalence disproportionately high in the northern states due to insecurity, poverty, maternal education gaps, and health system weaknesses. To address this challenge, Nigeria has developed ambitious strategies, including the Zero-Dose Immunization Recovery Plan (2023–2028) and the Zero-Dose Reduction Plan (ZDROP), which aim to cut zero-dose prevalence by 80% by 2028. Outreach delivery is central to these efforts, yet limited evidence has existed on its costs in Nigeria. This study aimed to estimate the costs of reaching zero-dose children through outreach delivery in three states in Nigeria, with a focus on ZDROP implementation.

Researchers used a retrospective bottom-up costing approach in Jigawa, Kaduna and Lagos states, including 57 health facilities across 8 local government areas. A qualitative assessment was also conducted alongside the costing to capture providers’ perspectives on the key barriers to vaccinating zero-dose children as well as their
recommendations to reduce zero-dose prevalence in their areas.

Key takeaways

• ZDROP facilities reached more children with Penta1 as well as with other antigens, particularly through outreach. This was true both in settings where caregivers received financial incentives for immunization, and where they did not.
• Increasing outreach delivery proved cost-efficient in settings where drivers of zero-dose prevalence can effectively be tackled by strengthening service delivery. In Jigawa, expanding outreach addressed awareness-related barriers, resulting in more children being reached and lower unit costs despite higher per-session expenditures.
• When multiple initiatives tackle the same drivers of zero-dose prevalence while failing to address other key barriers to immunization, diminishing returns are observed. In Kaduna, implementing ZDROP concurrently with other zero-dose reduction initiatives did not yield cost-efficiencies as all interventions targeted similar supply-side issues while demand-side barriers remained unaddressed. Lower unit costs were observed where only one initiative was implemented.
• Reaching zero-dose children in lower prevalence settings likely requires more resources. In Lagos, while the zero-dose targeted additional ZDROP outreach vaccinated more zero-dose children than regular outreach, it did so at a higher cost per Penta1 delivered.
• Only investing in strengthening service delivery may not be cost-efficient in settings where demand-side barriers are prominent. In Lagos, ZDROP outreach sessions reached more zero-dose children per session but at much higher unit costs, suggesting both the need for interventions better tailored to local drivers of zero-dose prevalence.
• What is cost-efficient in one setting may not be in another. Because root causes of zero-dose prevalence differ across contexts, aligning intervention strategies with context-specific barriers improves cost- efficiency by enabling interventions to reach more children at lower unit cost.

Thumbnail image credit: Shutterstock / pencilsmoka