Childhood vaccination rates have plummeted across hundreds of American communities, leaving a growing number of counties vulnerable to measles outbreaks as exemptions continue to rise, according to an extensive data analysis published by NBC News.
Public health experts recommend an immunization benchmark of at least 95 percent to maintain community protection against measles and stop the spread of the highly contagious respiratory virus. However, an increasing number of jurisdictions have fallen below that protective threshold as kindergarten vaccine waivers have climbed steadily for at least a decade, NBC News reported.
Sharp drops documented since 2019
Working alongside infectious disease specialists from Stanford University, journalists examined government records and Freedom of Information Act requests gathered between June and October 2026. The findings revealed that measles, mumps, and rubella, or MMR, coverage decreased by more than 5 percentage points in nearly 40 percent of examined counties between 2019 and the 2025-26 academic year.
The decline has accelerated in recent years. Roughly one in eight counties experienced a decline of more than 5 percentage points since 2024 alone, NBC News reported. Conversely, fewer than 2 percent of counties maintained steady levels with drops of 0.1 percentage points or less over the seven-year period.
The MMR vaccine remains highly effective at shielding both youth and adults from infection. Yet health officials warn that sagging coverage threatens to jeopardize the status of the United States as a nation that eliminated domestic measles transmission.
Gaps and inconsistencies in state tracking
The investigation revealed substantial hurdles in evaluating the national picture due to stark disparities in how state and local health departments gather and publish student immunization records. State rules also diverge widely regarding whether families can request exemptions on medical grounds, religious convictions, or personal beliefs.
Several state governments have halted or curtailed public reporting altogether. Florida stopped supplying kindergarten exemption figures after the 2021-22 school year, according to the report. Montana ended its tracking of vaccine coverage and exemption figures following the passage of House Bill 334 in 2021, which eliminated the legal requirement for state health authorities to monitor immunization metrics.
Other jurisdictions track data using different metrics or grade groupings. For instance, Illinois and New York monitor immunizations across entire elementary schools rather than kindergarten cohorts specifically. Wyoming tracks single-dose MMR coverage among toddlers aged 19 to 35 months, while Delaware and Rhode Island were unable to produce county-level tallies, supplying only statewide data.
Public health consequences remain uncertain
Public health researchers warn that as pockets of low coverage expand, communities face heightened chances of sudden disease clusters. Because measles spreads rapidly through airborne transmission, unvaccinated clusters can easily spark wider local outbreaks once an infection enters a school or neighborhood.
Whether state legislatures or federal authorities will take steps to bolster immunization mandates or standardize public health transparency remains to be seen as the school year progresses.
