Idaho’s low vaccination rates threaten US progress on measles control

With the highest rate of vaccine exemptions in the US and decreasing immunisation coverage, Idaho faces a rising risk of measles outbreaks amid a nationwide decline in childhood vaccination rates, raising concerns among health officials and clinicians.

As the US measles tally climbed to 3,134 confirmed cases by 3 September, Idaho entered the new school term with the weakest kindergarten measles protection in the country and the highest rate of vaccine exemptions. Federal and KFF data show 17.5% of Idaho children starting kindergarten were exempt from at least one required shot in 2025-26, while just 75.2% had completed the recommended measles, mumps and rubella course, far below the 95% level public health officials generally look for to prevent outbreaks. (cdc.gov)

The Idaho figures sit inside a broader national slide. The CDC said exemptions among US kindergartners rose to a record 4.2% from 3.6% a year earlier, while coverage fell for every vaccine it tracks at school entry. About 155,000 children nationally were exempt from one or more vaccines, and roughly 280,000 were at school without documentation showing they had completed the two-dose MMR series. Exemptions increased in 41 states and Washington, DC, and 24 states reported rates above 5%. (cdc.gov)

Idaho remains an outlier even in that worsening picture. KFF’s state breakdown shows almost all of the state’s exemption rate came from non-medical opt-outs: 17.0 percentage points were non-medical, compared with 0.4 points that were medical. Scientific American’s analysis of the CDC release found Idaho’s kindergarten MMR coverage has fallen about 15 percentage points over the past decade, from 89.1% in 2019-20 to 75.2% in 2025-26. By contrast, AP reported that Connecticut’s exemption rate was below 0.5%, while West Virginia posted the nation’s highest MMR coverage at 98.9%. Scientific American said only about 10 states now meet the 95% threshold. (kff.org)

The way Idaho handles exemptions helps explain part of the gap. State health guidance says parents can claim an exemption for medical, religious or “other” reasons, and that a non-medical exemption can be filed with a signed written statement. Another Idaho health department page says schools and day care providers must also tell families that those exemptions exist when communicating about immunisation rules. Medical Daily, comparing Idaho with West Virginia, noted that school vaccine requirements are set by states and highlighted Idaho’s 2025 Medical Freedom Act, which took effect in July 2025 and restricted many institutions from requiring a medical intervention as a condition of attendance or employment. (healthandwelfare.idaho.gov)

For clinicians, the numbers describe a change they say they already feel in consulting rooms. Noreen Womack, a paediatrician at St Luke’s Children’s Hospital, said she had never seen a case of pertussis until she began practising in Idaho and described caring for an infant with whooping cough who repeatedly turned blue during fits of coughing. She also said families had become “confused and torn” by misinformation and disinformation around childhood immunisation. Patrice Burgess, a Saint Alphonsus family medicine doctor, said the return of diseases once rarely encountered had been “heartbreaking” and told KREM that clinicians were having to “relearn some of these diseases”. Idaho’s own health department warns that measles, tetanus and whooping cough still circulate and that outbreaks of vaccine-preventable disease do occur in the state, while the CDC’s current measles dashboard lists Idaho among the jurisdictions reporting cases this year. (healthandwelfare.idaho.gov)

Doctors’ concern has been sharpened by the political row around vaccines. AP reported that paediatric infectious disease specialist James Campbell of the American Academy of Pediatrics blamed the latest decline on turmoil in federal policy, saying: “The root cause of this is primarily because there’s so much chaos and confusion in vaccination recommendation systems in the last year or so.” Even so, the immediate rules that families face at school registration are still largely written at state level, not in Washington, which means Idaho’s low coverage is tied not just to national messaging but to choices made closer to home. (ctinsider.com)

Other Western states are also near the top of the exemption rankings, though none is as high as Idaho. Becker’s Hospital Review, using KFF’s analysis of CDC data, listed Utah next at 12.7%, followed by Oregon at 11%, Arizona at 10.6% and Nevada at 8.7%. It said 30 states were above the national average, while five were below 1%: California, Connecticut, New York, Maine and West Virginia, though West Virginia’s exemption rules remain tangled in litigation. Scientific American noted that states which do not allow personal exemptions tend to report higher vaccination rates, but also cautioned that statewide averages can hide local pockets of susceptibility large enough to sustain an outbreak. (beckershospitalreview.com)

Idaho health officials say vaccines remain widely available despite the state’s exemption-friendly rules. The Department of Health and Welfare says routine childhood shots are offered to Idaho children under 19 at no cost or sharply reduced cost through participating providers and local public health districts, and children who are catching up can still be conditionally enrolled in school. Schools must file annual immunisation status reports with the state by 1 November, so the next official snapshot will come later in the autumn. Until then, the backdrop is a national measles year that has already overtaken the whole of 2025, with hundreds of thousands of children across the country lacking documented MMR protection as classes begin. (healthandwelfare.idaho.gov)