The number of foreign residents in Japan has risen rapidly, exceeding 3·7 million by the end of 2024—the highest on record. Although foreign residents represent less than 3% of the population, far lower than in Australia (30%), Canada (23%), and the United States (14%),1 anti-immigrant sentiment has intensified. During the 2025 upper-house election, some political parties pledged stricter foreign resident regulations. Major national newspapers reported that campaign speeches in several prefectures framed migrants as “burdens” on welfare and security systems, reflecting growing public unease over migration.2 Amplified by xenophobic narratives on social media, such rhetoric risks fostering suspicion toward migrants and discouraging research engagement.
In Japan, migrant health research now faces a chilling effect. Participants hesitate to join studies, fearing social or political repercussions. Municipalities and community organizations are increasingly reluctant to cooperate. Researchers, too, face heightened scrutiny that can affect ethics reviews and funding decisions. Such dynamics quietly erode the infrastructure necessary for evidence-based health research. In our longitudinal studies on Vietnamese migrants, recruitment was sustained only when participants felt safe and trusted the research context.3 Exclusionary climates therefore threaten the continuity of evidence building on migrant loneliness, mental health, infectious diseases, and disaster preparedness. Recent evidence also shows that migrants with lower social and political integration in Japan were more hesitant to accept COVID-19 vaccination,4 suggesting that hostile environments can undermine engagement in public health interventions.
International guidance underscores the ethical risks posed by politicized climates. The World Health Organization and the Council for International Organizations of Medical Sciences emphasize the duty to provide special protections for vulnerable populations.5 A stigmatizing political climate undermines these principles and destabilizes the research and non-profit sectors that support public health initiatives.
Japan's experience shows how politicized rhetoric can compromise research integrity and erode protections for vulnerable groups. Public health research should not be subject to shifting political tides. Safeguarding migrant health research requires coordinated efforts among policymakers, institutions, and the global health community. Reaffirming this commitment is crucial to maintaining ethical standards and protecting the integrity of migrant health research in Japan.
Declaration of interests
The authors have no conflicts of interest to declare.
Acknowledgements
This study received no external funding.
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