Measles continues to spread in Arizona and as kids are heading back to school, most classrooms across the state have immunization rates below the level recommended to prevent an outbreak.
Arizona has had 342 measles cases since last year — the highest tally the state has seen in more than three decades. The majority of those cases have been among unvaccinated kids under 18, according to the Arizona Department of Health Services.
The MMR vaccine provides strong, lifelong protection against measles. According to the Centers for Disease Control and Prevention, two doses of the vaccine are 97% effective at blocking the virus.
But measles is so contagious that about 95% of the population needs to be vaccinated to stop its spread.
Only a quarter of Arizona’s kindergarten classrooms hit that target last year, according to the Arizona Department of Health Services. In Greenlee, Mohave, La Paz and Yavapai counties, there were no schools reporting 95% immunity.
“That’s just a perfect environment for bigger outbreaks in the future,” said Will Humble, executive director of the Arizona Public Health Association.
The statewide average MMR vaccination rate among Arizona kindergarteners has not been 95% since the 2010-2011 school year, according to the Arizona Department of Health Services. As of the 2025-2026 school year, the average kindergarten vaccination rate statewide had fallen to 88%.
“Now that our vaccination rates are so bad in a lot of parts of the state, most county health departments are going to have to be prepared that through the rest of their careers there’s going to be sporadic measles outbreaks,” Humble said. “To make that not happen again, we’ve got to get our vaccination rates back up to where they need to be.”
Measles vaccines are required for Arizona schoolchildren, but the state allows exemptions for medical reasons or personal beliefs.
The rate of children needing medical exemptions from vaccines tends to be very steady year-to-year and is typically under 0.5%. But Humble said anti-vaccine skepticism has driven a notable rise in families seeking those personal-belief exemptions.
The increase has accelerated in the years since the COVID-19 pandemic. In the 2019-2020 school year, 5.4% of Arizona’s kindergarteners had personal-belief exemptions for at least one required vaccine. As of the 2025-2026 school year, the state’s personal-belief exemption rate was 9.9%.
According to the health policy research organization KFF, Arizona’s personal-belief exemption rate for school vaccinations is the fifth-highest in the country.
The American Academy of Pediatrics says assertions by vaccine skeptics that the MMR vaccine is as dangerous as the virus itself have been repeatedly disproven by science. The organization strongly recommends the MMR vaccine for children and warns that measles can cause pneumonia, brain swelling, long-term health complications or in rare cases, death.
The Arizona Department of Health Services lists vaccination rates by county and by school on its website.
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