Title : Learning from innovative border post vaccination outreach to tackle ZERO-DOES children of migrant communities in Cambodia

Background: Large migration flows between the Cambodian Thai borders for economic opportunities pose difficulties to provide and track immunizations among children of migrant worker communities, one of the four types of zero-dose communities in Cambodia. These children are often missed by routine services and routine data reporting systems. Using the Gavi Equity Accelerator Fund (EAF), the National Immunization Program (NIP) launched an innovative, locally tailored border post vaccination outreach in two northwest provinces during major holidays characterised by high population mobility. This case study presents findings and recommendations from implementation to inform future strategies for reaching zero-dose children of migrant communities.

Methodology: Immunization data for four rounds of implementation over the course of 2024 and 2025 was collected through standard paper-based tally sheets. In addition, interviews were conducted with key stakeholders (e.g. healthcare workers, caregivers) during a joint monitoring visit to one of three implementing districts in Banteay Meanchey province during the Cambodian New Year in April 2024 by the Provincial and district Expanded Programme for Immunisation (EPI) staff and Clinton Health Access Initiative (CHAI).

Results: The border vaccination outreach was conducted in April and October 2024 and April, and December 2025 during Cambodian national holidays spanning approximately 10 days across 3 districts in Banteay Meanchey province. Among 3,837 children over one year who vaccinated with any antigen, 4% were zero-dose children. The outreach provided integrated primary health care services, including nutrition and de-worming. Immunisation at the border site was successfully driven by NIP’s leadership, flexibility in implementing the program, and strong cooperation from the provincial administration. First, despite late notification from the national level, provincial EPI still managed to set up the campaign, albeit with less guidance and were able to reach 1,667 children (4% ZD) in year 1. Secondly, rather than implementing during working hours (8 am – 5 pm), provincial EPI seized the opportunity to operate during peak border mobility times (early morning and evening) in earlier sessions to avoid missed vaccination opportunities. Moreover, border tensions between Cambodia and Thailand limited border vaccination campaigns to a single round in early 2025. However, provincial EPI adapted border vaccinations to reach displaced communities, resulting in an additional round of border vaccination in 1 of 3 ODs in Banteay Meanchey, where 171 children (4.7% ZD) were vaccinated, all of whom were reached in displacement areas in Dec 2025. Lastly, the implementation also highlighted the importance of cross-ministerial collaboration. With border sites managed by the Ministries of Interior and Economy and Finance, additional engagement beyond a letter from the provincial governor is needed for effective inter-ministerial coordination.

Conclusion: Overall, the border vaccination outreach in Banteay Meanchey province demonstrated that with adaptive leadership and operational flexibility, hard-to-reach and displaced populations can be effectively vaccinated even under challenging conditions. However, sustaining and scaling these efforts will require more structured inter-ministerial coordination mechanisms, particularly given the multi-ministry governance of border sites. Establishing formal engagement channels beyond provincial-level correspondence will be critical to ensuring continuity, expanding coverage, and reducing the proportion of zero-dose children in border and displacement-affected communities.

Somontha is a Senior Analyst at Clinton Health Access Initiative, leading the implementation of the Equity Accelerator Fund (EAF) in Cambodia, funded through Gates Foundation. Somontha led monitoring, evaluation, and learning activities to strengthen immunization service delivery and reach under-vaccinated populations. Her work included coordinating implementation across provincial health departments, conducting field assessments to identify barriers to vaccination, developing operational guidance and performance monitoring tools, and documenting lessons learned. Through close collaboration with government and community stakeholders, she generated evidence to support adaptive program improvements, enhance equitable vaccine access, and inform strategies for increasing immunization coverage among vulnerable populations.