Background: Sustaining an effective evidence-based health intervention will maximize its impact on public health. Political and governmental reforms impacted on immunization program sustainability both positively and negatively. This study aims to explore the sustainability of polio immunization in a decentralized health system taking lessons learned from a polio eradication initiative in Indonesia.

Methods: We collected qualitative data through in-depth interviews with 27 key informants from various backgrounds at district, provincial, and national levels, consisting of frontline workers, managers, and Non-government Organizations (NGOs). We conducted thematic analysis and triangulated using document reviews. We also conducted member checking and peer debriefing to ensure trustworthiness.

Results: Competing priority was identified as the significant challenge to sustain government commitment for polio immunization and AFP surveillance during the transition toward a decentralized health system. Variation of local government capacities has also affected immunization delivery and commitment at the sub-national level government. The government reform has led to a more democratic society, facilitating vaccine rejection and hesitancy. The multi-sector partnership played a significant role in maintaining polio immunization coverage. Strong and continuous advocacy and campaign were essential to raising awareness of the community and policymakers to keep polio in the agenda and to maintain the high polio immunization coverage.

Conclusion: Competing priority was the major factor affecting high polio immunization coverage during the decentralization transition. Strong advocacy is needed at every level, from district to national level, to keep polio immunization prioritized.