A public health milestone the United States guarded for over a quarter-century has slipped away, and the reasons behind it should concern every parent.
The United States has lost its measles elimination status, researchers with knowledge of the decision confirmed to KFF Health News on Saturday, as reported by CBS News. The determination by the Pan American Health Organization came after the country recorded more than 5,400 measles cases so far this year, more than double last year's total.
The Pan American Health Organization serves as the World Health Organization's regional office for North and South America. The agency is set to hold a news conference on Tuesday.
Under the World Health Organization's standard, a country is considered to have eliminated measles if there are "no locally transmitted measles infections or outbreaks lasting 12 months or longer." This year marks the first time since 2000 that the United States has failed to meet that bar.
Data from the Centers for Disease Control and Prevention show that roughly a third of this year's cases are linked to outbreaks that began in 2025 and never stopped spreading. After a three-decade record set last year, the CDC has tallied 5,412 cases so far in 2026, with more than 590 hospitalizations and at least six measles-related deaths.
Some states have reported additional fatalities beyond the federal count. The worst outbreak has been in Pennsylvania, where state health officials have recorded more than 1,500 cases and seven deaths tied to the disease this year, while New York and Wisconsin have each reported one death.
Measles cases have now been confirmed in 45 states and Washington, D.C. Very few corners of the country have been spared.
Dr. Cline Gounder, the network's medical correspondent, explained that a country or region loses its elimination status once population immunity falls far enough for the disease to keep spreading on its own. Where vaccination rates are high, a single case or a small outbreak soon fizzles out, but with this many gaps in immunity, there can be "ongoing chains of transmission," Gounder said.
"It means that we're at risk of being exposed to measles and getting measles if we're not vaccinated," Gounder said. "It means ERs and pediatricians need to consider measles in anyone with a fever and rash, whether they've traveled overseas or not. And we may now become an exporter of measles to other countries."
Dr. Omer Awan, a trained epidemiologist and senior public health contributor for Forbes, called the loss a setback for the nation's public health infrastructure. His frustration centered on the fact that the remedy has been available for decades.
"It's frustrating and heartbreaking ... because we have the tools to fight this. The tool is the MMR vaccine, which we know is 97% effective at preventing the onset of measles," Awan said. "It'd be one thing if we didn't have the tools to fight this, but the tools are at our disposal, we just aren't using the tools that can help us mitigate the spread and beat measles."
Federal health officials have struck a similar note. "The measles elimination designation is not what protects Americans. Vaccination does," CDC Director Erica Schwartz said in a statement this week, according to The Associated Press.
A country earns elimination status by showing there is no local spread of the disease and no outbreak lasting more than a year. According to PAHO, the most reliable way to keep that status is to maintain a vaccination rate of 95% or higher.
Countries are also expected to run sensitive surveillance systems that catch cases quickly, keep adequate laboratory capacity and guarantee a rapid response to outbreaks. Data on all of these measures must be submitted to and verified by the organization.
For the United States to curb its outbreaks and win back elimination status, Awan said, vaccination rates must climb again. He said countering misinformation and ramping up vaccination campaigns would be central to that effort.
The challenge is real. Data show childhood vaccination rates have fallen in many American communities in recent years, often dropping below the threshold needed to keep measles at bay.
Gounder noted that much of the power to reverse that trend rests with state lawmakers. She pointed to school vaccine rules as the clearest lever.
"States set the school vaccine rules. Nine states made opting out of vaccination easier in 2025. States ending nonmedical exemptions saw kindergarten vaccination rise 2 to 4 points," Gounder said.
She closed with a pointed reminder about the calendar. "Most legislatures reconvene in January. Your state lawmakers will write next year's exemption rules."
The nation's long fight against measles is well documented. The United States began collecting national measles data in 1912, according to the CDC, and about 6,000 measles-related deaths were reported each year during the first decade of record-keeping.
Between 1953 and 1963, nearly every American child caught measles before turning 15, with an estimated 3 to 4 million infections and tens of thousands of hospitalizations each year. In those years, 400 to 500 people, most of them children, died of the disease annually, according to the CDC.
That changed in 1963, when the measles vaccine first became widely available. Cases fell sharply, and several generations of Americans grew up without ever encountering the disease.
By 1981, reported cases had dropped by 80% compared with the previous year, the CDC said. The nation was officially declared to have eliminated measles in 2000.
The United States held that status for more than 25 years, though not without flare-ups. In 2015, an outbreak among unvaccinated people was traced to overseas visitors at Disneyland in Southern California, and a 2018-19 outbreak in New York was eventually contained through public health measures that included curtailing vaccine exemptions.
Those episodes, however, were a fraction of the spread now under way. In 2025, the CDC counted 2,289 cases, the most the country had seen in more than three decades, along with 245 hospitalizations, mostly among children, and three deaths, with infections confirmed in at least 44 states.
That record did not stand for long. By October 2026, the total had more than doubled, and it climbed past 5,000 earlier this month.
Nearly all of the cases have involved people who were not vaccinated. The CDC said 43 new outbreaks, defined as three or more related cases, have been reported so far in 2026.
Measles ranks among the most contagious infectious diseases, and those who are unvaccinated face the greatest risk. CDC data show that 96% of people infected in 2026 were either unvaccinated or unsure of their vaccination status, while only 2% of cases involved people who were fully vaccinated.
Many patients recover, but measles can cause severe infections of the lungs and brain that may lead to cognitive problems, deafness or death. Medical research has shown that two doses of the measles, mumps and rubella (MMR) vaccine are extremely safe and effective at protecting against the disease.
Some Americans, including babies, pregnant women and people with weakened immune systems, cannot be vaccinated and depend on the immunity of those around them. Awan said these groups will bear "the brunt of the consequences" of the wider spread. "They will be the ones that are most vulnerable to getting infected and experiencing the complications," such as pneumonia or encephalitis, Awan said.
The road back is clear, even if it will not be quick. A country regains elimination status only by ending local transmission and staying free of outbreaks for at least 12 months, which means the choices families make at the pediatrician's office, and the exemption rules state legislators write when they reconvene in January, will decide how soon the United States can reclaim a distinction it held for 26 years.
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