A critical role of navigator for vulnerable migrants in health emergency: overcoming administrative barriers to COVID-19 vaccination in Japan.

Introduction: Migrants face significant barriers in accessing healthcare, particularly during public health emergencies such as the COVID-19 pandemic. In Japan, the residency-based healthcare system posed administrative challenges for migrants, especially undocumented individuals, in obtaining vaccination vouchers-a prerequisite for receiving COVID-19 vaccines. The COVID-19 Vaccination Information Center for International Citizens (COVIC) was established to bridge this gap by offering multilingual support and direct casework assistance. Methods: This study employed a case study design, analyzing 275 inquiries involving 418 migrants who sought assistance from COVIC between September 2021 and March 2022. Using Castañeda et al.'s framework on migration and health, administrative barriers were examined, and COVIC's role as a navigator was evaluated. Descriptive statistics were used to assess COVIC's impact on vaccine access. Results: The majority of migrants seeking assistance (38.5 %) were undocumented, and 91.3 % of them lacked a vaccination voucher before contacting COVIC. The intervention facilitated voucher issuance for 73.8 % of migrants who inquired about it. While COVIC successfully helped all short-term and mid-to-long-term residents obtain vouchers, only 54.2 % of undocumented migrants were able to receive one, reflecting persistent systemic exclusions. Conclusion: COVIC played a crucial role in mitigating administrative barriers, yet structural limitations prevented full healthcare access for undocumented migrants. These findings underscore the need for standardized administrative policies, integrated navigator programs, and inclusive healthcare strategies to enhance equitable access for migrant populations in future health crises.