A year ago, Florida's surgeon general said he would spearhead an effort to end all vaccine mandates in schools. A new study predicts that policy, if enacted in the Sunshine State, could unleash a wave of measles nationwide on a level not seen in the last 50 years.
Hundreds of pediatric deaths could be anticipated from measles within the next five years across the country, according to the projections published Monday in the Proceedings of the National Academy of Sciences (PNAS), a peer-reviewed journal.
"We're soon going to start seeing children developing severe disease and dying of measles," said co-author Abba Gumel, a professor in the Department of Mathematics at the University of Maryland.
Using mathematical models and data from the recent Texas outbreak, adapted to Florida’s current conditions, the study shows how relaxing school rules for vaccines could make measles common again in Florida and "reignite transmission across the United States."
Under a worst-case scenario, “Florida will experience a pronounced measles outbreak within three to five years,” as vaccination rates dip to 82%.
According to the CDC, 88.9% of Florida kindergarteners were fully vaccinated in the 2025-26 school year.
The PNAS study uses a a more generous current figure of 91.6% vaccination in Florida, based on the CDC average for the state from 2011-2025.
“The estimated epidemic peaks will exceed those of any year in the United States since 1977,” with infections “ranging between 260 and 315 measles cases per 100,000 children,” said the study. Adult infection rates are projected at about half the rate of children.
Before a measles vaccine was available, about 500 people died each year in the nation from the disease, which can cause fatal brain swelling and pneumonia.
A vaccine to prevent measles was first licensed in the United States in 1963, and the combined measles, mumps and rubella (MMR) vaccine came on the market in 1971.
But uptake was lax in some areas. The US counted 57,345 measles cases in 1977. After that, public health officials began a campaign to vaccinate more children, and the disease rate dropped significantly.
Measles cases are rebounding again as more parents opt their children out of the measles, mumps and rubella (MMR) vaccine, even though major medical groups insist it is safe and effective at preventing measles.
Effect on children
This year, the United States is seeing the highest number of measles cases in decades -- 3,659 as of Sept. 29, according to the Centers for Disease Control and Prevention -- with recent deadly outbreaks affecting Pennsylvania and Texas.
So far in 2026, Florida has documented 162 cases of measles and no deaths.
"Repealing the mandate would really, really negatively impact public health as a whole in Florida, but especially the children there,” said Alice Oveson, a PhD student in applied math at the University of Maryland and lead author of the study.
“The most important result from our projections is that this vaccination is so necessary for the protection of children,” she said.
Already, some counties in Florida are far below the recommended threshold of 95 percent vaccination coverage to maintain herd immunity against measles, which is one of the most contagious diseases.
In Sarasota County, just about 79 percent of kindergarteners are up to date on their shots, according to Department of Health data.
Ira Longini, a biostatistician at the University of Florida who was not involved in the research, said the predictions of case counts and deaths could be “a large overestimate.”
The study described its methodology as “an age-structured mechanistic model tailored to Florida’s population to quantify the potential impact of removing the MMR school entry vaccination mandate on measles outbreak risk.”
Longini said that’s not necessarily the right approach.
“A simple, deterministic random mixing model with just children and adults is not able to make accurate projections of the number of cases and deaths over time because people simply do not mix randomly on a state level,” Longini said. “Measles comes in sporadic clusters as the coverage goes down and introductions occur.”
Instead, a type of modeling that looks at separate habitat areas, called a stochastic patch model, or an agent-based computer model is needed “to predict cases over time, because that is how a disease like measles spreads,” Longini said.
Still, Longini said he agrees with the overall message in the report. Florida’s vaccine policies, championed by Surgeon General Joseph Ladapo, would erode the already low vaccination rate, he said.
“Yes, we will see more cases and deaths in both children and adults due to increasing sporadic outbreaks as coverage in children declines and even in vaccinated adults,” he said.
“The only way to prevent this is to get coverage in children back up to an average of 95% and vaccinate vulnerable adults, but the key is to increase coverage in children and keep it there,” Longini said.
