Millions of U.S. measles cases forecast over 25 years if shots decline

“Our country is on a tipping point for measles to once again become a common household disease,” said Nathan Lo, a Stanford physician and author of the study published in the medical journal JAMA.

At current state-level vaccination rates, the model predicts that measles could become entrenched, resulting in “hundreds of thousands of cases, where deaths are commonplace and hospitalizations are happening all the time,” said Lo, who researches the transmission of infectious diseases and the impact of public health interventions.

The estimates are based on a simulation of what would happen in the United States under various vaccination rates for children. A small uptick in vaccination — a 5 percent increase in state-level rates — would prevent huge increases in measles cases, the study found.

But Lo said he fears that the most likely scenario is that childhood vaccination rates will continue to decline and the cumulative number of infections will rise sharply.

Hesitancy to accept covid-19 vaccines has led more parents to question routine childhood vaccinations. Ongoing state policy debates about school vaccination requirements and Health Secretary Robert F. Kennedy Jr.’s interest in reexamining the childhood vaccine schedule could substantially reduce immunization coverage, he said.

“This is a warning of what our future could look like,” said Mujeeb Basit, a professor and expert on modeling and disease spread at UT Southwestern Medical Center in Dallas. Basit was not part of the study.

The measles cases will accumulate over time, Basit said. “To re-bend that curve, it’s going to take a lot of time to revaccinate so many people.”

The U.S. already has recorded about 800 measles cases in the first 3½ months of 2025, the largest number in a single year since 2019.

The numbers continue to grow, according to data from the Centers for Disease Control and Prevention and state health departments. Montana last week reported its first measles cases in 35 years.

The majority of the infections have been reported in a West Texas outbreak that has led to the deaths of two children. A third death in New Mexico is also linked to the outbreak.

Amid the continuing spread of the infectious disease, most Americans have encountered false claims about the measles vaccine, and many aren’t sure what the truth is, according to a KFF poll released Wednesday. More than half the adults surveyed expressed uncertainty about whether to believe false assertions, such as that the measles vaccine is more dangerous than the disease — claims that Kennedy has amplified.

In the decade before a measles vaccine was introduced in 1963, an estimated 3 million to 4 million people in the U.S. were infected each year, 400 to 500 people died, 48,000 were hospitalized and 1,000 suffered swelling of the brain, or encephalitis, according to the CDC.

But in 2000 the U.S. was finally able to declare measles “eliminated,” a term that means no continuous spread for more than a year. Cases and outbreaks still occur because of international travel, typically with an under-immunized U.S. traveler returning from a country where measles is endemic.

The modeling also looked at scenarios for other vaccine-preventable diseases that have been eradicated. If vaccination rates drop 35 percent, rubella will probably become endemic, the researchers concluded, while polio has a 50-50 chance of becoming endemic if vaccination drops by 40 percent. Even lower vaccine levels would be required before outbreaks and sustained transmission of diphtheria returned, according to the researchers.

For the new research, scientists used state vaccination, birth and death rates to find their results. They estimated current vaccination coverage for measles at 87.7 percent to 95.6 percent. To prevent measles outbreaks, 95 percent of a community must receive two doses of the measles, mumps and rubella (MMR) vaccine.

Based on what scientists know about the epidemiology of measles, one of the most contagious diseases on Earth, they forecast how it would spread from one community to another and how quickly it could spread regularly at increased rates throughout the country.

The study did not take into account the difference in vaccination rates within a state, the authors said. Nor did it account for changes in immunization rates when infections increased because of an outbreak, which occurred during the covid pandemic, Basit said. But even the most conservative estimates underscore the severe consequences if measles reestablishes itself in the U.S., the authors said.

Measles outbreaks are surging globally, with Romania last year reporting the largest number of cases among 53 countries in Europe and Central Asia, according to the World Health Organization. Romania, with a population of about 19 million, had more than 30,000 cases in 2024, followed by Kazakhstan with about 28,000 cases. Romania’s recent measles surge is linked to declining vaccination rates, vaccine hesitancy, and disruptions in the health system during the pandemic, health experts have said.

In the U.S., public health and infectious-disease experts have been talking for months about ways to combat false claims and misinformation about vaccines. On Thursday, an infectious-disease research center at the University of Minnesota announced an initiative to provide a coordinated response.

“People who care about preventing needless suffering and death from vaccine-preventable diseases have watched the current measles outbreak and Health Secretary Robert F. Kennedy Jr.’s rhetoric about vaccines with rising alarm,” said Michael Osterholm, director of the university’s Center for Infectious Disease Research and Policy, which launched the Vaccine Integrity Project.

Initial funding for the project is from a foundation established by Christy Walton, an heir to the Walmart fortune, Osterholm said. The group does not plan to accept funding from industry.

The goal is to address key vaccine issues “if the U.S. government vaccine information becomes corrupted … or the system that helps to ensure [vaccines’] safety and efficacy are compromised,” Osterholm said in a news briefing.

Osterholm cited an example in Minnesota, where Republican lawmakers introduced a bill that classifies mRNA vaccines as “weapons of mass destruction” and criminalizes their manufacture, distribution and possession.

The cutting-edge mRNA technology was behind the rapid development of lifesaving covid vaccines.

“Is anybody at the federal government level going to respond to activities like that?” Osterholm said. “That’s a question I think we are left to at this point, unanswered.”

The group will be led by an eight-member committee chaired by Margaret Hamburg, a former Food and Drug Administration commissioner, and Harvey Fineberg, past president of the National Academy of Medicine.