Florida’s vulnerability to measles is approaching a critical tipping point, according to an analysis published this week in PNAS.
The coverage rate of the measles, mumps, and rubella (MMR) vaccination among Florida kindergarteners has fallen over the past decade. It is now low enough that a measles exposure in some schools would likely lead to an outbreak, which could have devastating consequences since one to three of every 1,000 children who become infected with measles will likely die from respiratory and neurologic complications.
Measles is the most contagious disease known to humans. According to the Centers for Disease Control and Prevention (CDC), if one person has it, nine out of 10 people of all ages around him or her will also become infected if they are not protected. And the World Health Organization says that one infected person can transmit the disease to as many as 18 other people.
A mathematical model developed at the University of Maryland (UMD) shows that if Florida removes its requirement that public school students receive the MMR vaccine, as proposed by the state’s surgeon general, the state could see an even sharper decline in the vaccination rate, leading to dozens, if not hundreds, of deaths in children in the following five to 10 years.
“As someone who has lost a child, not to a disease, but I have lost a child, that’s not something I could wish on anyone,” said lead author Alice Oveson, a PhD student in UMD’s applied math program.
As someone who has lost a child, not to a disease, but I have lost a child, that’s not something I could wish on anyone.
Several measles outbreaks within the United States have resulted in more than 3,600 confirmed cases in 2026, the most seen in 35 years. Pennsylvania announced a fifth measles-associated death today; the individual lived in Lancaster County, the epicenter of the state’s outbreak.
However, if vaccination coverage in Florida increased even a percentage point or two among either children or adults, Oveson told CIDRAP News, it would substantially reduce the risk of measles-related deaths among Florida kids.
Measles in Florida could be the worst in half a century
Using data from the 2025 measles outbreak in Gaines County, Texas, Oveson and UMD mathematician Abba Gumel, PhD, created a transmission model using Florida data on demographics, MMR coverage, and contact rate. The contact rate is the average number of interactions a person has with others based on their age and community size.
While Gaines County is younger and more rural than the state of Florida, the probability of an unvaccinated person catching measles after an exposure remains the same. That allowed Oveson and Gumel to assess potential outcomes if Florida ended its MMR school vaccine mandate.
For the 2025-26 school year, CDC data show that Florida’s MMR vaccination rate for kindergarteners is 88.9%. Under the worst-case scenario, in which coverage fell to 82%, the model shows that the state would have a pronounced measles outbreak within five to 10 years. In this worst-case scenario, the state’s disease level is predicted to exceed that of any year in the United States since 1977, with estimated infections ranging from 260 to 315 measles cases per 100,000 children.
However, if Florida’s kindergarten vaccination rate remains at 88.9%, the analysis found that short-term interventions such as isolation and masking can substantially reduce the epidemic burden. The vaccination rate required to prevent measles outbreaks is 95%.
What surprised Oveson most is that the mathematical model showed that although Florida is one of the oldest states—with 80% of its population above age 40—vaccinating one child in the state is three times more effective at reducing transmission than vaccinating one adult.
This is partly because immunity to measles is higher among older people, but also because the disease spreads more efficiently among children, who tend to have closer physical contact with each other.
A model is an educated guess, not a crystal ball
The UMD model falls “woefully” short in a few key aspects, said Matthew Ferrari, PhD, director of Penn State’s Center for Infectious Disease Dynamics.
Grouping all Floridians into people under and over age 18 is too simplistic and ignores specific risks to infants below vaccine age, Ferrari said. In addition, Florida is a large, geographically diverse state, and measles spikes during the winter and early spring—two other aspects the study doesn’t consider.
Also, to be considered fully vaccinated against measles, people need two doses of the MMR vaccine, Ferrari noted, but the model characterizes vaccination as just a single dose. And he called the findings on masking and isolation “speculative.”
Models are inaccurate by definition. But they give you an idea of what can happen.
“This paper adds nothing to the operational understanding of measles or measles control,” he said.
Despite these limitations, which the authors largely acknowledge, Andrew Pavia, MD, a pediatric infectious disease epidemiologist at the University of Utah, said that the UMD analysis is still useful for policymakers.
He said the results are plausible, though they shouldn’t be taken as gospel, partly because some elements of chance are difficult to factor in. For example, he noted that the biggest measles outbreaks over the past year have been in Texas, Utah, and Pennsylvania, while other parts of the United States that have very low MMR coverage rates have yet to experience big measles outbreaks.
“Models are inaccurate by definition,” Pavia said. “But they give you an idea of what can happen.”
The crisis is already here
The low end of the UMD model estimates there will be dozens of direct pediatric deaths from measles. But because measles can cause immune amnesia, in which an infection wipes out a significant amount of someone’s pre-existing immune memory, Pavia said there might be additional deaths in Florida if school vaccine requirements are removed.
“You’re [possibly] going to see more deaths from pneumococcal pneumonia, more deaths from rotavirus, and other diarrheal diseases,” he said.
Ultimately, a statistical model isn’t necessary to know that a crisis is on the horizon, said Michael Osterholm, PhD, MPH, director of the University of Minnesota’s Center for Infectious Disease Research and Policy, which publishes CIDRAP News.
You’re [possibly] going to see more deaths from pneumococcal pneumonia, more deaths from rotavirus, and other diarrheal diseases.
Osterholm pointed out that, in 2025, Canada reported 5,462 measles cases. Proportionally, that would be like the United States having 45,000 cases in a single year.
“That’s America’s future…you don’t even have to make it up as a worst-case scenario to scare people,” he said. “This is reality now.”