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Persistent excess mortality in post-pandemic Japan: current evidence, methodological limitations, and future
Hiroshi Kusunoki1, Ryota Sakai2, Yumi Watanabe3
1Department of Internal Medicine, Osaka Dental University, Hirakata, Japan.
Frontiers in Public Health
|July 8, 2026
Summary
Japan faces persistently high excess mortality post-COVID-19, with nearly 100,000 annual deaths. This review explores contributing factors and highlights data limitations for future research on mortality trends.
Area of Science:
- Public Health
- Epidemiology
- Demography
Background:
- Japan experiences sustained excess mortality years after COVID-19 emergence.
- Mortality increased significantly from 2022, despite high vaccination rates and Omicron variant predominance.
- Potential factors include aging, healthcare access changes, delayed treatment, and psychosocial stress.
Purpose of the Study:
- To examine persistent excess mortality in Japan.
- To illustrate methodological limitations using COVID-19 booster vaccination data.
- To advocate for improved data infrastructure for future analyses.
Main Methods:
- Narrative review of existing literature.
- Analysis of excess mortality trends in Japan.
- Examination of ecological and observational studies on booster vaccination.
Main Results:
- Excess mortality remains elevated in Japan, approaching 100,000 deaths annually.
- Some studies suggest associations between booster vaccination and excess mortality, but causality is not established.
- Methodological limitations hinder definitive conclusions regarding specific interventions.
Conclusions:
- Persistent excess mortality in Japan requires further investigation beyond direct COVID-19 impact.
- Robust, linked individual-level data and advanced analytical frameworks are crucial for accurate future evaluations.
- Causality between repeated booster vaccinations and excess mortality cannot be concluded from current evidence.
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