Measles was declared eliminated from the United States 25 years ago. Now, the Centers for Disease Control reports major outbreaks of the virus happening across the country.
The CDC counted 1,288 cases of the highly contagious viral illness in 2025 so far, or three times more than last year. Those numbers are the highest recorded since the early 90s. This comes as vaccination rates in the country, and in Idaho, continue to fall.
“If that continues, then the number of children who are not immune and are susceptible to measles builds up to a sufficient number that when a measles case is introduced, then it spreads like wildfire,” said infectious disease physician and researcher at Stanford Nathan Lo.
He and his colleagues published a study in the Journal of the American Medical Association this spring modeling the resurgence of diseases under declining vaccination rates.
“Under a scenario with 10% decline in MMR vaccination. We estimate about 11 million cases of measles over 25 years,” he said.
“Classic estimates say that we should maintain immunity around 95%, in the low to mid 90s to reliably prevent resurgence of measles,” Lo added.
Data from the Idaho Department of Health and Welfare show all routine vaccines amongst children have been steadily declining in the state, following a national trend. At 79%, schools in Idaho report the lowest rate of mumps, measles and rubella vaccinations among kindergartners in the country.
Those numbers don’t include home-schooled students, who are also less likely to be vaccinated.
Idaho Health and Welfare State epidemiologist Christine Hahn said that data may not reflect the whole picture, as its based on school documentation.
“It doesn't necessarily mean that the child is unvaccinated. It means that the parent does not want to report that information to the school,” she said. “if you look at the National Immunization Survey, which is a random digit dial survey across the country, including Idaho, we're actually much closer to the average.”
The CDC reports measles vaccination rates in children are at 88% in the state, or 4% lower than the national average, still below rates needed to prevent the return of measles.
“There has been an increase in vaccine hesitancy, concern about safety of vaccines, concern about whether they're necessary and that that has increased since the pandemic,” Hahn said.
A recent poll showed that measles misinformation is spreading.
“We could do better with our childhood immunization rates. Not all of our kids are protected when they enter kindergarten so we know we could see outbreaks in our schools,” she said.
Measles is not just contracted at school. During the summer, IDHW warns the virus can spread in large venues like concert halls.
“What we're thinking about right now and we're trying to message out is travelers: If you're traveling somewhere, make sure that you know your child's immunization status,” Hahn added.
Researcher Lo said the key finding of recent study is that measles is at a tipping point, set to become a common household disease again. That could lead to many childhood hospitalizations and deaths related to measles.
“For those children that have complications and even die from this infectious disease, it's really unimaginable,” the researcher said.
The highly contagious respiratory disease can lead to serious complications, like brain damage in young children and vulnerable people.
“It's scary to think [that] these types of clinical complications could happen again here,” Lo added. “It is all preventable.”
Before vaccines became available in 1963, about 48 000 people were hospitalized with cases of measles annually, with 400 to 500 people dying each year.
One in five children infected by measles in 2025 was hospitalized. The largest outbreak occurred in Texas. No cases were found in Idaho this year.
