When Japan scaled back its vaccine programs in response to safety concerns and public skepticism, the results provide a data-rich natural experiment in what happens when immunization rates drop—and the findings aren't encouraging.
The Nature analysis examines several Japanese vaccine policy shifts over recent decades, offering lessons particularly relevant as vaccine hesitancy rises globally.
Japan's experience includes some notable examples:
HPV vaccine suspension: In 2013, Japan suspended active recommendation of the HPV vaccine following reports of adverse events. While the vaccine remained technically available, the loss of government recommendation caused uptake to plummet from around 70% to below 1%.
The result? Japan now faces significantly higher rates of cervical cancer in cohorts that missed vaccination compared to countries that maintained their programs. The reported adverse events that triggered the suspension have not been definitively linked to the vaccine in subsequent research, suggesting the policy response may have been disproportionate to the actual risk.
Measles vaccination gaps: Japan also experienced periods of reduced measles vaccination coverage, leading to outbreaks that required subsequent catch-up programs to control.
What makes Japan's experience valuable for policy analysis is the quality of their health data. Japan maintains excellent disease surveillance and health records, allowing researchers to draw relatively clear causal connections between vaccination rate changes and disease outcomes.
The key insight isn't particularly surprising, but it is quantified: when vaccination rates drop below herd immunity thresholds, disease incidence rises in predictable ways. What's less obvious is how difficult it can be to restore public confidence once it's damaged.
Japan only resumed active HPV vaccine recommendation in 2022—nine years after the suspension—despite accumulating evidence of safety. That's nearly a decade of cohorts with low vaccination coverage, translating to increased cancer burden for years to come.
The policy implications extend beyond Japan. The article appears in Nature at a moment when vaccine hesitancy is rising in multiple countries, driven by various factors including social media misinformation, political polarization, and erosion of trust in public health institutions.
Several lessons emerge:
Precautionary principle has costs: Suspending vaccine programs "out of abundance of caution" sounds responsible, but creates its own risks. The question is always about balancing known vaccine risks against disease risks—not about whether risks exist at all.
Public confidence is fragile: Vaccination programs depend on trust. Once damaged, that trust can take years or decades to rebuild, during which disease burden accumulates.
Communication matters enormously: How public health authorities respond to safety signals determines whether concerns escalate into sustained vaccine hesitancy or get resolved through transparent investigation.
Now, it's important to note that vaccine safety monitoring is crucial and appropriate. Adverse event reporting systems exist for good reasons, and investigating safety signals is responsible public health practice.
The challenge is calibrating responses appropriately—taking safety concerns seriously without overreacting in ways that create larger public health harms.
Japan's experience suggests that once you suspend active vaccine recommendation, the political and social dynamics make it very difficult to reverse course, even when evidence supports safety. The lesson for other countries might be to invest heavily in robust safety monitoring and transparent communication before crises emerge, rather than relying on policy suspension as a primary response tool.
The universe doesn't care about our policy debates. The epidemiology follows from the vaccination rates, and the data from Japan shows what happens when those rates drop.
The question is whether other countries will learn from Japan's natural experiment, or conduct their own.
