Florida could face major measles resurgence if school vaccine mandate ends

Clinical takeaway: Continue to strongly recommend MMR vaccination and address vaccine hesitancy proactively. This modeling study suggests that maintaining high childhood vaccination coverage remains the most effective strategy for preventing future measles outbreaks.

Measles was declared eliminated in the US in 2000, but outbreaks have increased as vaccination coverage has declined in some communities. In 2025, Florida officials proposed eliminating school-entry vaccine requirements, raising concerns about whether current immunity levels are sufficient to prevent renewed transmission.

A Florida-specific mathematical model suggests the state may already be below the vaccination threshold needed to reliably prevent sustained measles transmission. Researchers calibrated the model using data from the 2025 measles outbreak in Gaines County, Texas, and incorporated Florida's demographics, contact patterns, and historical MMR vaccination rates. Current estimated MMR coverage was approximately 92% among children and 93% among adults.

The analysis found that relatively small reductions in childhood vaccination could have outsized effects on outbreak size because children account for a disproportionate share of measles transmission. Under a worst-case scenario, repeal of school-entry mandates could reduce childhood MMR uptake to roughly 82%, leading to outbreak peaks of 260-315 measles cases per 100,000 children within 3 to 5 years. Adult outbreak rates were projected to reach 135-160 cases per 100,000.

Long-term simulations projected recurring outbreaks over decades and suggested measles could become endemic in Florida if vaccination coverage continues to decline. The model also projected substantial pediatric mortality over time. Increasing adult vaccination coverage helped reduce transmission risk, but the authors found that vaccinating children was more than three times as effective per dose at lowering outbreak potential.

"Maintaining or improving MMR vaccination coverage is essential to prevent measles from reestablishing endemic circulation within the state and potentially spreading to the broader United States," the authors wrote.

Source: Oveson A, Gumel AB. (2026 Sep 28) Proc Natl Acad Sci U S A. Projected effects of removing school-entry vaccination requirements on measles transmission in Florida