Assessing the zero dose reduction operational plan strategy and its effects on immunization performance in priority local government areas in Nigeria a mixed methods implementation design

The Zero-Dose Operational Plan (Z-DROP) was implemented in 100 Local Government Areas (LGAs) across 18 states in Nigeria, targeting regions with the highest number of zero-dose children aged 0–23 months. This study aimed to describe the development and deployment of Z-DROP, identify barriers and facilitators to its implementation, and assess its impact on immunization performance. A mixed-methods implementation design was used. Deductive thematic analysis of secondary data informed the description of Z-DROP development and key implementation factors. Quantitative analysis involved paired sample t-tests comparing mean differences in the number of children aged 0–11 months and 12–23 months vaccinated with Penta1, Penta3, and MCV1 vaccines before and during implementation. Findings showed a statistically significant increase in vaccination among children aged 12–23 months for Penta1 ( t (100) = -5.88, p < .001) and MCV1 ( t (100) = -3.98, p < .001) during implementation compared to the pre-implementation period. However, no significant improvement was observed for MCV1 among children aged 0–11 months ( t (100) = -1.30, p = .10). Key facilitators included the application of the Identify, Reach, Measure, Monitor, and Advocate (IRMMA) framework, the use of immunization performance indicators to identify zero-dose and under-immunized populations, and strong engagement of program managers and stakeholders at all levels. Major barriers included inadequate manpower and funding, insecurity in certain regions, challenges reaching urban poor and slum populations, and vaccine hesitancy or refusal in some communities. In conclusion, we observed improved immunization coverage, particularly among older children (12–23 months). However, gaps remain in reaching younger infants, highlighting the need for strengthened strategies to address resource limitations, access challenges, and community resistance to achieve broader immunization equity.