A Disease Once Eliminated Is Roaring Back
The United States eliminated measles in 2000, meaning the virus was no longer continuously circulating within the country's borders. It was one of the great triumphs of public health, the culmination of decades of vaccination campaigns that pushed immunization rates above the threshold needed to maintain herd immunity. Twenty-six years later, that achievement is unraveling at alarming speed.
As of mid-February 2026, the Centers for Disease Control and Prevention has confirmed 982 measles cases across the United States, with outbreaks reported in close to half of all states. Texas has been particularly hard hit, with clusters emerging in multiple regions including the Hill Country, where six cases were confirmed in a single household in Bandera County. All six individuals were unvaccinated. The pattern is consistent with every other outbreak: measles is finding its way into communities where vaccination rates have dropped below the critical threshold.
Public health officials are increasingly concerned that measles, one of the most contagious diseases known to medicine, may be serving as a canary in the coal mine. If vaccination rates have fallen low enough for measles to spread, other vaccine-preventable diseases may not be far behind.
Why Measles Is the First Domino
Measles occupies a unique position among infectious diseases. It is extraordinarily contagious, with a basic reproduction number estimated between twelve and eighteen, meaning that a single infected person will, on average, infect twelve to eighteen susceptible individuals in an unvaccinated population. By comparison, influenza typically infects two to three people, and the original strain of SARS-CoV-2 infected about two to three.
This extreme contagiousness means that measles is the first disease to break through when vaccination rates decline. It requires roughly ninety-five percent population immunity to maintain herd protection, one of the highest thresholds of any infectious disease. When coverage drops even a few percentage points below this level, outbreaks become not just possible but inevitable.
The current situation represents a predictable consequence of a decade-long decline in childhood vaccination rates across the United States. Exemption rates from school vaccination requirements have risen steadily, driven by a combination of misinformation about vaccine safety, ideological opposition to government mandates, and logistical barriers to accessing vaccination services. The result is a growing population of susceptible individuals, predominantly children, concentrated in communities where exemption rates are highest.
The Human Cost of Measles
Measles is often dismissed as a mild childhood illness, a perception that reflects the success of vaccination in making the disease rare rather than any change in its severity. In reality, measles is a serious disease that can cause pneumonia, encephalitis, and death. Prior to the introduction of the measles vaccine in 1963, the disease killed roughly five hundred Americans annually, hospitalized forty-eight thousand, and caused about one thousand cases of encephalitis, which can result in permanent brain damage.
Among the 982 cases confirmed in 2026, hospitalizations and complications are already being reported, though detailed national statistics are still being compiled. The Texas outbreaks have been described by infectious disease experts as completely preventable, a characterization that underscores the frustration felt by public health professionals watching a conquered disease return.
Children under five and immunocompromised individuals who cannot be vaccinated are at greatest risk. These populations depend entirely on the vaccination of those around them for protection, a concept known as herd immunity. When community vaccination rates fall, the most vulnerable members of that community lose their shield.
The Diseases Waiting in the Wings
The measles-mumps-rubella vaccine, commonly known as MMR, protects against three diseases simultaneously. Two doses of the vaccine are ninety-seven percent effective at preventing measles and similarly effective against mumps and rubella. When MMR vaccination rates decline, all three diseases lose their population-level protection simultaneously.
Mumps, which causes painful swelling of the salivary glands and can lead to serious complications including orchitis, a swelling of the testes that can cause infertility, as well as meningitis, encephalitis, and permanent deafness, is already seeing sporadic increases. Unlike measles, which produces a distinctive rash that makes cases easy to identify, mumps can present with milder symptoms that are easily overlooked, potentially allowing it to spread more widely before being detected.
Beyond the MMR triad, public health experts are watching several other vaccine-preventable diseases with concern. Hepatitis B, which can cause chronic liver infection and liver cancer, requires a multi-dose vaccination series that many children may not be completing. Pertussis, commonly known as whooping cough, has already shown cyclical increases in recent years. Varicella, or chickenpox, which can cause severe complications in adults and immunocompromised individuals, is another potential concern as vaccination rates erode.
The Structural Drivers of Declining Vaccination
Understanding why vaccination rates are falling requires looking beyond any single cause. The anti-vaccination movement, amplified by social media platforms that have proven unable or unwilling to limit the spread of health misinformation, is a significant factor but not the only one.
Structural barriers play an equally important role. Access to primary care has declined in many rural and low-income communities, making it harder for families to obtain routine childhood vaccinations even when they want them. The complexity of the recommended vaccination schedule, which involves multiple visits over several years, means that any disruption to a family's access to healthcare can result in incomplete immunization. The COVID-19 pandemic caused widespread disruptions to routine childhood vaccination that have not been fully recovered.
Political dynamics have also shifted. Vaccination requirements for school entry, once a bipartisan consensus, have become increasingly contested, with state legislatures in several states expanding exemption provisions or weakening enforcement. The politicization of vaccination during the COVID-19 pandemic appears to have generalized to all vaccines, eroding trust in immunization programs that had nothing to do with the pandemic.
What Public Health Officials Are Recommending
The response to the current measles outbreak involves both immediate and long-term strategies. In the short term, health departments in affected areas are conducting contact tracing, identifying exposed individuals, and offering post-exposure vaccination, which can prevent or reduce the severity of disease if administered within seventy-two hours of exposure.
For the longer term, public health officials are calling for a renewed commitment to childhood vaccination. The CDC continues to recommend that all children receive two doses of MMR vaccine, with the first dose at twelve to fifteen months of age and the second at four to six years. Adults who are unsure of their vaccination status are encouraged to consult their healthcare providers, particularly those born after 1957, as people born before that year are generally considered immune due to natural exposure during a time when measles circulated freely.
Healthcare providers are being urged to use every patient encounter as an opportunity to check and update vaccination status, a strategy known as opportunistic vaccination. Schools are being encouraged to strictly enforce existing vaccination requirements and minimize the use of non-medical exemptions.
A Preventable Crisis
The current measles resurgence is, by any objective measure, entirely preventable. The vaccines exist, they are safe, they are effective, and they are widely available. Two doses of MMR vaccine provide ninety-seven percent protection against a disease that, in the pre-vaccine era, infected virtually every child in the country by age fifteen.
What is lacking is not the science but the societal commitment to applying it. Every case of measles in 2026 represents a failure of public health infrastructure, health communication, or political will. The nearly one thousand cases confirmed so far this year are not a natural disaster. They are a policy outcome, and they foreshadow a broader unraveling of vaccine-preventable disease control that could take years or decades to reverse.
The experts are unequivocal in their assessment. Measles is the warning signal. If the underlying causes of declining vaccination are not addressed, diseases that the United States has controlled for decades will continue to return, bringing with them suffering that was supposed to belong to another era.
This article is based on reporting by MIT Technology Review. Read the original article.
