Arizona has one of the lowest levels of kindergarten vaccination coverage in the United States, making schoolchildren in the state more vulnerable to disease outbreaks than other parts of the country, new federal data show.
Of 48 states and the District of Columbia that are included in the new U.S. Centers for Disease Control and Prevention data, only Idaho, Wisconsin, Minnesota and Utah had lower levels of MMR, measles, mumps and diphtheria vaccine coverage for kindergarten students. Kansas and Montana were not included in the Aug. 17 report.
The percentage of U.S. kindergarten schoolchildren who are vaccinated against measles with the MMR, measles mumps and rubella, vaccine is 92.4%, or nine out of 10 kindergarten kids, which sounds pretty good
and indeed, the vast majority of parents and guardians of kids in U.S. kindergartens are still making sure their schoolchildren are vaccinated against measles.
However, the levels are not enough to provide community protection against the highly contagious measles virus.
Epidemiologists say that the threshold of kids vaccinated needed to provide community protection, sometimes known as herd immunity, needs to be high enough to protect weaker people, which in the case of kids would include children with weakened immune systems, such as those undergoing chemotherapy. Herd immunity is the level of vaccination in a community at which diseases have a minimal chance of spreading. Herd immunity for measles is 95% because the measles virus is so contagious.
Arizona's measles coverage for kindergarten kids was, at 87.4%, significantly worse than the national average and far below herd immunity.
States with the highest, most protected levels of kindergarten MMR coverage in the data were (in order), West Virginia, Connecticut, Maine, New York and Mississippi. West Virginia, Connecticut, Maine and New York, unlike Arizona, do not allow any nonmedical exemptions to school vaccine requirements.
All states allow for medical exemptions to school vaccine requirements, but there's a patchwork of different rules on who can get exempted for non-medical reasons. Arizona allows parents to exempt their children for "personal belief" and religious reasons, as do many other states, including New Mexico, Texas, Utah, and Colorado. The percentage of kindergarteners exempted from vaccines for nonmedical reasons has been rising nationally and in Arizona, too.
The federal data was released at a time when the United States is experiencing a resurgence of measles, and when President Donald Trump and U.S. Health and Human Services Secretary Robert F. Kennedy Jr. are attempting to reshape the childhood vaccine schedule and sending mixed messages about vaccine safety, moves that major medical organizations say are undermining public health policy and scientific evidence.
'I wasn't surprised. It's just disappointing'
Measles is often called the canary in the coal mine for vaccine-preventable disease outbreaks.
Measles is the most contagious vaccine-preventable human virus, so cases are a warning sign that in areas with low immunization coverage, other dangerous vaccine-preventable diseases like polio and diphtheria, could return.
Arizona kindergarten classes were among the least immunized in the country for other school required vaccines, too, including diphtheria, pertussis and tetanus; polio; and Hepatitis B, the federal data say.
"I wasn't surprised. It's just disappointing," said Will Humble, a former state health director and executive director of the Arizona Public Health Association, speaking about Arizona's results. "Even though there are outbreaks of measles, it doesn't appear to have inspired more parents to get their kids vaccinated."
Arizona has experienced a major resurgence of measles: the 221 cases reported in 2025, primarily fueled by an outbreak in Mohave County on the Arizona-Utah border, was a 30-year high number and the third-highest number of measles cases in the U.S. that year, according to the Johns Hopkins Bloomberg School of Public Health measles tracker.
As of Aug. 18, there had been 122 measles cases reported to the Arizona Department of Health Services in 2026, including 27 in Maricopa County, which includes the Phoenix area.
Whooping cough hit Arizona hard in 2025, too, with nine outbreaks, one death and the highest number of cases in 12 years, state data shows. Whooping cough, often known as pertussis, is preventable with the DTaP or diphtheria, tetanus and pertussis vaccine.
Kennedy's leadership and vaccine skepticism likely had an effect on waning vaccination rates statewide, but it's not the sole cause of the decline in Arizona, Humble emphasized.
He blames the drop on three factors: Arizona policy allowing religious and personal belief exemptions to school vaccine requirements; prior state overregulation of the federal Vaccines for Children program, which reduced provider enrollment statewide; and pre-existing skepticism about science and vaccines that has grown under Kennedy's influence.
New CDC data: AZ now has the 5th lowest childhood MMR vaccination rate in the country. That's not a culture war stat — it's an impending outbreak. Measles herd immunity needs 95% coverage. I'll be watching Maricopa County numbers when school year data lands this fall.
— Brian Murray (@BrianMurrayAZ) August 19, 2026
Anti-vax sentiments not the only reason for Arizona's declining rates
An Arizona Department of Health Services analysis of kindergarten MMR immunization released earlier in the summer found that only one in four schools with kindergarten classes in Arizona had herd immunity against measles. Some counties were better than others.
Mohave County was the worst. No schools with kindergartens in the county had herd immunity in the 2025-26 school year. A county push for vaccination during a massive outbreak centered in the rural area of Colorado City that began in August 2025 and did not end until the spring of 2026, but Humble of the Arizona Public Health Association said that school vaccine data is gathered in the fall, so an uptick of immunizations in Colorado City schools would not be reflected in the recent data.
Also, Humble said that Mohave County was one of the hardest-hit areas when it came to providers exiting the federal Vaccines for Children Program,which provides vaccines to kids who are uninsured, underinsured and those covered by Medicaid, which is a government health insurance program for people who are in lower income households or who have disabilities.
"If it's harder to find a place to get your kids vaccinated, that's an unforced error, as they say in tennis," Humble said.
Statewide, the program went from 1,200 providers in 2015 to about 600 in 2022, Humble wrote in a 2022 blog post.
Vaccines for Children in Arizona "continues ongoing efforts to recruit additional providers to the program," Arizona Department of Health Services spokesperson Magda Rodriguez wrote in an email. Statewide, the program had 568 enrolled providers as of Aug. 21, according to data provided by both the state and the Maricopa County Department of Public Health.
The state Health Department has been making a significant effort to expand Vaccines for Children and grow its network of providers, Jennifer Tinney, program and policy director for The Arizona Partnership for Immunization, TAPI, confirmed.
"They are working really hard with providers, and talking to them to find out challenges and barriers," Tinney said.
One way that Arizona could boost its school vaccination rates is to prohibit religious and personal belief exemptions to school vaccines, but Humble said that would require a significant change to the composition of the Republican-dominated Arizona Legislature.
California banned all nonmedical exemptions to school vaccines in 2016 after a measles outbreak at Disneyland, and the state's school immunization percentages immediately went up. California's measles coverage for kindergarteners in the 2025-26 academic year was 95.7%, which is above herd immunity, the CDC data show.
President Donald Trump on Aug. 10 issued an executive order titled "Delivering Gold Standard Childhood Vaccine Recommendations for Americans" that calls for reducing the number of childhood vaccines, and also for spacing them out. More than 200 medical organizations, including the American Academy of Pediatrics, the American Medical Association, and the Autism Science Foundation denounced the order for making changes without any scientific evidence to support them.
Rep. John Garamendi, D-California, and Senate Democratic Leader Chuck Schumer, D-New York, on Aug. 17 wrote a letter signed by 90 other members of Congress, including Rep. Adelita Grijalva, D-Arizona, that demands Trump rescind his executive order, which they say "overrides decades of scientific evidence and sows fear, chaos, and confusion."
The executive order as of Aug. 20 had not changed any recommendations or school or child care immunization requirements from the Arizona Department of Health Services. In a Aug. 14 letter to providers, state health officials recommend following the childhood immunization schedule issued by the American Academy of Pediatrics (AAP), which is "supported by extensive scientific research and evidence, and are tailored to the unique needs of the populations we serve. "
Reach health-care reporter Stephanie Innes at stephanie.innes@usatodayco.com or follow her on X: @stephanieinnes or on Bluesky: @stephanieinnes.bsky.social.
This article originally appeared on Arizona Republic: Arizona among lowest in US for kindergarten vaccination rates
