The United States has lost its measles elimination status. Here’s what that means and who’s most at risk.

The United States has lost its measles elimination status, researchers with knowledge of the decision confirmed to CBS News partner KFF Health News on Saturday.

The Pan American Health Organization’s decision came after the United States recorded more than 5,400 cases of measles so far this year, more than double last year’s total. The Pan American Health Organization is a regional office of the World Health Organization, covering North and South America. The agency is expected to hold a news conference Tuesday.

A country is considered to have eliminated measles if there are “no locally transmitted measles infections or outbreaks for 12 months or more,” according to the World Health Organization.

The United States failed to meet that standard for the first time since 2000. According to data from the Centers for Disease Control and Prevention, about a third of this year’s measles cases are linked to outbreaks that began in 2025 and continue to spread.

After 30 years of experience 2,242 cases last yearThe CDC has documented 5,412 cases so far in 2026, resulting in more than 590 hospitalizations and at least six measles-related deaths, with some states reporting additional deaths.

The largest outbreak has been in Pennsylvania, where state health officials have reported more than 1,500 cases and seven deaths associated with the disease this year. New York and Wisconsin each reported one death.

Measles cases have been confirmed so far this year in 45 states and Washington, D.C.

What does losing measles elimination status mean?

A country or region loses its measles elimination status once population immunity is decreasing enough that the spread of the disease can be sustained, explained CBS News medical correspondent Dr. Céline Gounder. When a country has measles elimination status and a high vaccination rate, a measles case or small outbreak will disappear quickly. But when there are so many gaps in population immunity, there can be “continuous chains of transmission,” Gounder said.

“This means we are at risk of being exposed to and contracting measles if we are not vaccinated,” Gounder said. “This means that emergency rooms and pediatricians should consider measles in anyone with a fever and rash, whether they have traveled abroad or not. And we could now become an exporter of measles to other countries.”

Dr Omer Awan, qualified epidemiologist and senior public health contributor for Forbes, said the loss of measles elimination status is a setback for the country’s public health infrastructure.

“It’s frustrating and heartbreaking… because we have the tools to combat this. The tool is the MMR vaccine, which we know is 97% effective in preventing the onset of measles,” Awan said. “It would be one thing if we didn’t have the tools to fight this, but the tools are available to us, we’re just not using the tools that can help us mitigate the spread and defeat measles.”

How can the United States regain measles elimination status?

A country achieves measles elimination status by ensuring that there is no local spread of the disease or an outbreak that lasts more than a year.

PAHO says the best way to maintain measles elimination is to maintain a vaccination rate of 95% or higher. Countries should also have sensitive surveillance systems to quickly detect cases, laboratory capacity and a rapid response to epidemics. Data on these trends must be submitted and verified by the organization.

For the United States to curb outbreaks and return to measles elimination status, it must return to higher vaccination rates, Awan said. He said fight against misinformation and the rise in power vaccination campaigns would be key to this effort.

Data shows childhood vaccination rates have declined In many communities in the United States in recent years, often below the necessary threshold to help prevent measles outbreaks.

Gounder also noted that lawmakers can create policies that lead to increasing vaccination rates.

“States set the rules for school vaccinations. Nine states made it easier to opt out of vaccination in 2025. States ending non-medical exemptions saw vaccinations in preschools increase by 2 to 4 points,” Gounder said. “Most legislatures reconvene in January. Your state legislators will write next year’s exemption rules.”

Measles in the United States

The United States began collecting national data on measles in 1912, according to the Centers for Disease Control and Prevention. Approximately 6,000 measles-related deaths were reported annually during the first decade of this data collection.

In the decade between 1953 and 1963, almost all American children caught measles before the age of 15, with an estimated 3 to 4 million people infected each year and tens of thousands hospitalized, according to the CDC. During those years, 400 to 500 people, mostly children, died from measles each year.

Then, in 1963, the measles vaccine was first introduced became widely available. The numbers began to decline sharply and several generations of Americans grew up without ever being touched by measles.

By 1981, reported measles cases had dropped 80 percent from the previous year, the CDC said. The country was officially declared to have eliminated measles in 2000.

The United States has maintained its elimination status for more than 25 years. This does not mean that there have been no cases: in 2015, an epidemic that spread among unvaccinated people has been traced to out-of-state visitors to Disneyland in Southern California, and to a 2018-19 epidemic in New York was ultimately contained by public health measures, including reduce exemptions for vaccines. But those spikes represented only a fraction of the spread currently seen in the United States.

The country recorded 2,242 cases of measles in 2025, according to CDC data, linked to 48 separate outbreaks. The CDC reported 245 hospitalizations, mostly among children, and three deaths from measles last year. Infections have been confirmed in at least 44 states. This is the highest number of cases the country has seen in more than three decades.

That the record was broken in 2026while the United States recorded more than double that number of cases in October – a total that surpassed 5,000 earlier this month.

Almost all cases involved unvaccinated people. Measles-related deaths have been reported in Pennsylvania, New York and Wisconsin.

The CDC said 43 new outbreaks — defined as three or more linked cases — have been reported so far in 2026, while about a third of cases reported this year are linked to ongoing outbreaks since 2025.

Who is at risk of contracting measles?

Measles is one of the most contagious infectious diseases. Those who are not vaccinated against the disease are at the greatest risk of contracting it. CDC data shows that 96% of people infected with measles in 2026 were not vaccinated against measles or were unsure of their vaccination status; only 2% of cases involved fully vaccinated people.

Although many people recover, measles can cause serious infections of the lungs and brain that can 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 in protecting against measles.

Some people – including babies, pregnant women or people with weakened immune systems – cannot get vaccinated against measles and therefore rely on population immunity to prevent the disease from spreading. Awan said these groups of people will bear “the brunt of the consequences” of the increased spread of measles.

“They are the ones who will be most vulnerable to infection and complications,” such as pneumonia or encephalitis, Awan said.