Vaccination has an unusual political problem: Its greatest achievements are invisible. 

When a vaccine prevents measles, there is no dramatic event to observe. A child does not become sick. A parent does not rush to an emergency department. A hospital bed remains empty. A family does not have to experience the fear and uncertainty that accompany serious infection. 

The success of prevention is precisely that nothing happens. This makes prevention difficult to communicate because people tend to judge risk through what they can see, remember, and experience.

Vaccines work only when people can access them and enough people continue to use them.      

The invisibility of prevention creates a reversal in how risk can be perceived. For instance, a parent may hear about a possible vaccine adverse event today, while the complications of measles remain an abstract possibility. 

Take the case of polio. Years ago people were well aware that polio infection could cause disability because they knew so many people were affected. Today, people are more fearful of vaccination than the disease — in part because the disease has become unfamiliar. 

The vaccine becomes visible while the disease becomes invisible.    

The Warning Signs Are No Longer Theoretical     

One of the most contagious human infections, measles, is returning in countries that once ended transmission. The World Health Organization (WHO) and UNICEF reported that 57 countries experienced large or disruptive measles outbreaks during 2025. The United States confirmed more than 2,000 measles cases, its highest annual total since measles elimination was declared in 2000. Across the states, there were 48 outbreaks, mostly among people who were unvaccinated or whose vaccination status was unknown. 

Canada provides an even more striking example. After achieving measles elimination in 1998, Canada reported more than 5,000 measles cases with rash onset in 2025, compared with an average of about 91 cases a year before. Before 2025, WHO identified Canada as a country that had eliminated measles, meaning that continual, endemic transmission had stopped. But in 2026 similarly high numbers of measles cases have been reported in Canada. 

Europe has faced the same warning. WHO and UNICEF reported 33,998 cases across Europe and Central Asia in 2025. The European Centre for Disease Prevention and Control continues to identify community transmission and immunity gaps as important risks.

These numbers should not be read as evidence that vaccines have suddenly stopped working. 

The escalation of measles in wealthy countries shows something more basic and more uncomfortable: Vaccines work only when people can access them and enough people continue to use them.      

Vaccines work for measles by making sure a substantial number of people in the community have been vaccinated. Canada notes that coverage of about 95% is needed to sustain measles elimination. Globally, however, only 77% of children received both recommended measles doses in 2025, well below the level required to prevent outbreaks.      

Why People Aren’t Vaccinating     

Why aren’t people vaccinating today, even though vaccination was more common only a few decades ago? 

People who hesitate to vaccinate often have genuine questions about safety. Others have had poor experiences with health care institutions. Some face practical barriers to vaccination. Others have been exposed to misleading information. Many may simply underestimate the risk of diseases they have never seen.

This distinction matters because often public health officials identify people who do not vaccinate as part of a group who exhibit vaccine hesitancy. The term “vaccine hesitancy,” however, can hide several different reasons people remain unvaccinated. 

One challenge is cultural and another problem is structural. For instance, someone who prefers not to vaccinate due to a deeply held belief faces a different challenge compared to           someone who supports vaccination but cannot get an appointment, has lost their child’s vaccination records, works during clinic hours, or does not know that a catch-up dose is needed. 

Relatedly, a parent who distrusts government because of previous experiences with public institutions differs from a parent who has simply forgotten a routine appointment, a parent who is influenced by religious or cultural beliefs, or a parent who is worried about side effects based on a previous adverse experience.

The challenge is therefore larger than persuading people to believe in vaccines. It is about understanding how people form judgments about risk and how those judgments are shaped by institutions, communities, politics, media, and personal experience. 

A vaccine can become a symbol of trust or distrust in government rather than what it actually is: a medical intervention whose benefits and risks can be assessed using evidence. 

It is a broader question about whether health systems and societies can maintain the collective conditions that allow vaccination to protect populations over time.

Public-health agencies therefore need to ask a more useful question: What is preventing this particular person or community from being vaccinated? The answer might be misinformation. It might be distrust. It might be cost. It might be inconvenience. It might be political identity. It might be complacency. Often, several factors will operate at the same time.

The response should reflect that complexity.

Vaccination Is a Science Policy Issue

Vaccination is often presented as a purely medical decision. But governments decide how immunization programs are financed and organized, what information is provided to citizens, how vaccination records are maintained, how schools and healthcare systems coordinate, how safety concerns are investigated and how outbreaks are managed. Political leaders also influence the public climate in which these decisions are made.

This is where vaccine policy can become particularly vulnerable to polarization. Once vaccination becomes a marker of political identity, evidence can be interpreted through partisan loyalties. A vaccine can become a symbol of trust or distrust in government rather than what it actually is: a medical intervention whose benefits and risks can be assessed using evidence. 

A trustworthy health system is one that gives people good reasons to trust it.

For example, a vaccination campaign may be linked to support for a particular political party. A public health agency can become associated with a particular political ideology, which is often led by charismatic leaders. Also, vaccine mandates can become framed as symbols of government control; vaccine refusal can become a form of political resistance; or vaccine acceptance can become a marker of political allegiance.

Overcoming these variables requires a deeper trust in government leadership and a dimming of political polarization. Scientists and public-health authorities should be able to defend strong evidence while acknowledging uncertainty where uncertainty exists. Patients should be able to ask difficult questions without being dismissed. Governments should be transparent about how recommendations are developed and how vaccine safety is monitored.

Trust is not the same as obedience. A trustworthy health system is one that gives people good reasons to trust it.

We Need to Make Prevention Visible Again

If part of the problem is that people have forgotten what vaccine-preventable diseases look like, then public health needs to restore that memory, but without resorting to fear.

I am not suggesting that we must frighten children with graphic images or to shame parents who are uncertain. Rather, schools, museums, documentaries, public health campaigns and personal testimony can be mobilized to teach the history of infectious disease. 

Older generations who lived through epidemics can tell their stories. Patients and families affected by vaccine-preventable diseases can help explain what the statistics mean in human terms. Medical education can connect current vaccination recommendations with the history that produced them. Public health agencies could use campaigns featuring older generations who lived through epidemics to share their experiences. 

When it works, people forget what it prevented.

The objective is not to frighten people into compliance. It is to make the value of prevention visible.

This matters because public health policy has an unusual communications challenge: The healthier a population becomes, the less evidence people have that the intervention is working. 

The Health System Needs to Become Easier to Navigate

There are key structural changes that involve better administration of public health efforts that can make a big difference for vaccination campaigns. 

Governments should invest in reminder and recall systems to help families remember when vaccinations are due and follow up with those who miss appointments. They should provide accessible vaccination records so families and health care providers can easily determine which vaccines a child has received and which are still needed. 

Clinics need to be flexible to accommodate parents and caregivers who cannot attend during standard working hours. These efforts also must involve catch-up vaccination programs to help children who have fallen behind the recommended schedule return to it. 

And the vaccinations should be distributed by trust health officials in settings that make patients feel safe and cared for, like schools or community centers. In other contexts, primary care settings or pharmacies might be the most convenient and trusted places to learn about and receive vaccines. 

The lesson is straightforward: Not everyone who is unvaccinated needs to be persuaded. Some simply need the system to make vaccination possible.                                                            

We Should Not Wait for Disease to Remind Us

We should not have to relearn the value of prevention through another epidemic.

The U.S., Canada, and Europe demonstrate that the re-emergence of vaccine-preventable disease can happen in societies with advanced science, substantial resources, and sophisticated health care institutions.                          

The task now is not simply to persuade people to vaccinate. It is to ensure that the absence of disease remains understood as the achievement of prevention, not as proof that prevention is no longer necessary.

Because the greatest danger of a successful vaccine programme is also its greatest triumph: When it works, people forget what it prevented.

And if we allow that memory to disappear completely, the diseases we defeated may be waiting for their opportunity to introduce themselves again.