No federal floor on childhood vaccine exemptions — kindergarten MMR coverage fell to 92.5 percent in 2024-25 and US measles elimination status comes up for review in November 2026

What is happening?

The United States has no federal minimum standard for school vaccine exemptions. Which children may skip a required vaccine, and on what grounds, is decided by each state. The constitutional basis was fixed in 1905, when the Supreme Court in Jacobson v. Massachusetts upheld compulsory vaccination as an exercise of the police power of a state — a power held by the states and not by the federal government.

Under that arrangement the national numbers have moved one way for five years. Two-dose MMR coverage among children entering kindergarten was 92.5 percent in the 2024-25 school year, down from 95.2 percent in 2019-20 and lower in each year between. DTaP, polio and varicella coverage sat in the same band, 92.1 to 92.5 percent, in 2024-25.

The exemption rate went the other way. 3.6 percent of kindergartners held an exemption from at least one required vaccine in 2024-25, a record, against 3.3 percent in 2023-24, 3.0 percent in 2022-23 and 2.6 percent in 2021-22. That is about 138,000 children. The rate rose year over year in 36 states and the District of Columbia, 17 states stood above 5 percent, and Idaho was highest at 15.4 percent.

The growth is entirely nonmedical. Medical exemptions have stayed near 0.2 percent for a decade, while nonmedical exemptions on religious or philosophical grounds rose from 2.0 percent in 2014 to 3.4 percent in 2024.

Measles is the consequence already being counted. The United States recorded 2,289 confirmed measles cases in 2025, the most since 1992, across 49 outbreaks in 45 jurisdictions against 16 outbreaks in 2024. 93 percent of patients were unvaccinated or of unknown vaccination status, 11 percent were hospitalized, and three people died, two of them children. The country was declared to have eliminated measles in 2000, a status defined as the absence of endemic domestic transmission for 12 months or more. In November 2025 the regional review committee of the Pan American Health Organization classified the United States as sustained with major concerns and withdrew the same status from Canada. The final review of the United States is scheduled for November 2026.

Whose problem is this?

The people who decide and the people who bear the result are separated by a border. A legislature that widens an exemption answers to the voters of one state, while measles moves through whoever is susceptible next, in that state or the one beside it.

Where does this problem end?

The boundary matters because the science is not what is contested and the remedy is not undiscovered. Every state already requires vaccines for school entry. What varies is how easily a family can be excused from that requirement, and nothing above the states sets a floor under that variation.

What is the state now, and what should it be?

Now

Should be

The target is published and it is a single number. Healthy People 2030 sets kindergarten two-dose MMR coverage at 95 percent, and 95 percent is also the level conventionally cited as the point at which measles stops finding a chain of susceptible people to move through. National coverage in 2024-25 was two and a half points below that line, and the county sample sat about four points below it in 2023-24.

How big is it?

About 138,000 children. That is the number of kindergartners who held an exemption from at least one required vaccine in the 2024-25 school year, and it is the only recent national count that measures the exemption mechanism directly.

It is not the same as the number of children unprotected against measles, and the two counts pull in opposite directions. An exemption from one required vaccine does not mean a child lacks MMR, so 138,000 overstates the measles-specific gap. In the other direction, about 280,000 kindergartners lacked documentation of two MMR doses in 2023-24, which was 7.3 percent of that cohort, and the broader count includes children who were never exempted but arrived incompletely vaccinated or without records. The 2024-25 update to that broader figure was not obtained in this round.

Neither count reaches the place where measles actually spreads, which is the county and the school. In a sample of 2,066 counties across 33 states, average kindergarten coverage fell from about 94 percent in 2017-18 to about 91 percent in 2023-24, and coverage declined in 78 percent of those counties.

The harm already counted is smaller and separately measured. In 2025 there were 2,289 confirmed measles cases nationally, 11 percent of patients were hospitalized and three died. The largest single event was the West Texas outbreak of 2025, with 762 confirmed cases, 99 hospitalizations and two deaths, both of them school-age children who had not been vaccinated.

Under what conditions does it arise?

1. The authority was assigned to the states and never shared. Jacobson v. Massachusetts upheld compulsory vaccination in 1905 as an exercise of the police power of a state. Every school entry requirement in the country descends from that holding, and there is no federal counterpart to amend.

2. The federal government holds the money but not the pen. Vaccines for Children has bought vaccines for eligible children since 1994 and lowered the cost barrier. It does not reach exemption law, because the spending power and the regulatory power were separated at the outset.

3. The exemption is a form, and each state prices the form. Where a state removed the nonmedical ground the rate fell, and where a state merely added an education module and a signature the rate also fell, by less. A study of state-level data reports that each additional percentage point of nonmedical exemption is associated with about 1.1 fewer percentage points of MMR coverage, with an R-squared of about 0.66.

4. The threshold is local but the number that gets reported is national. Measles needs roughly 95 percent coverage in the population a case actually reaches. A national average of 92.5 percent is compatible with many counties comfortably above the line and many well below it, and the average is what appears in the annual release.

5. The result crosses the border that the decision does not. A state that keeps a narrow exemption cannot hold an elimination record of its own, because outbreaks travel and the status under review is national and verified internationally.

6. The signal arrives years after the choice. Coverage falls quietly, and nothing happens until a case reaches a community that has drifted below the threshold. By then the exemptions that made the outbreak possible were filed in earlier school years.

What has been tried?

Every attempt that moved the exemption rate was made by a state, and every attempt made at the federal level moved something else. That division is not an accident of this decade. It is the shape the 1905 holding left behind, and no later step has changed it.

What was found?

Why is it still unsolved?

Institutional gap — there is no federal rule to enforce, and the absence is not an oversight but the settled allocation of power.

This is not a written rule going unenforced. Under Jacobson v. Massachusetts the requirement to vaccinate for school entry is an exercise of state police power, so every requirement in the country is a state requirement. A federal agency can buy the vaccine, recommend the schedule and count the coverage, and it has done all three for decades. It cannot set the terms on which a family is excused, because that is not a power it holds.

The second part is that the number which would raise an alarm is the wrong shape. Measles spreads through whoever a case actually reaches, which makes the threshold a county threshold and a school threshold. What gets published is a national average, and a national average of 92.5 percent can describe a country uniformly two and a half points short or a country split between places well above the line and places far below it. The one study that looked found the second picture, in 33 states.

The third part is that the cost lands on people who did not make the choice, and it arrives long after the choice can be reversed. Coverage drifts down for years without an event. Then a case arrives, and those who are hurt include infants too young for a first dose and children who cannot be vaccinated at all, none of whom filed anything. A slow harm with no identifiable moment produces no deadline, and this one has produced none in the eleven years since 2014.

What observation would mean it is solved?

Candidates — (a) national kindergarten two-dose MMR coverage returns to 95 percent or above and stays there for several consecutive school years (b) the share of counties below the level at which measles stops spreading falls, measured across all states rather than a 33-state sample (c) the Pan American Health Organization revalidates the elimination status of the United States in November 2026 and again in the years after.

(a) alone hides the thing that matters. A national average can return to 95 percent while the counties that produced the outbreaks stay where they are. Protection is local, so an average that improves by improving the already-safe places would read as solved and change nothing on the ground.

(b) is the right shape and the data is not there. The only county-level analysis opened here covers 33 states, and the 17 it leaves out sit outside its design rather than outside the world. Until that measure runs nationally there is no way to watch the quantity that actually governs transmission.

(c) is a judgment about a 12-month record, not about coverage. Elimination status turns on whether endemic domestic transmission persisted for 12 months, and that depends on how many cases arrived from abroad and where they landed as much as on how many children are susceptible. A year with few importations could pass the review with coverage unchanged, and one unlucky chain could fail it after coverage had begun to recover.

The nonmedical exemption rate is tracked above as an indicator and is not listed here as a candidate. It counts paper: it measures forms filed, not doses given, and children who are behind on the schedule or whose records never arrived are invisible to it, so in 2023-24 that broader group was more than twice the size of the exempted one. It also sits on a different axis from the three above. Coverage, the county threshold and the elimination review are levels that an agency or a review committee has already defined, while how a state writes its exemption requirements is a policy choice each legislature makes, and this document does not support any of the available designs over the others. The three candidates have to be read together, and (b) is the one currently missing.

What is it connected to?

Fills with researchthe standing of federal public health rulemaking after recent Supreme Court decisions, state and local health department funding, measles control in the countries that send travelers to the United States, and the wider question of how far a federal minimum standard can reach into an area held by the states. Relation type and evidence grade were not confirmed in this round.

What these sources do not say

• Why the 2025 national total differs across sources. Figures of 2,144, 2,231, 2,288 and 2,289 circulate for the same year. The two opened directly agree closely, at 2,288 and 2,289, and the spread appears to come from snapshot date and from whether probable cases are counted alongside confirmed ones — but no source opened here states its counting basis.
• The 2024-25 count of children without documented two-dose MMR. The 2023-24 figure of about 280,000 has no successor in what was opened. That is a gap in this research round, not necessarily in the published record.
• What the 2026 case counts are as of a stated date. Neither article carrying a 2026 figure gives its snapshot date, which is why 2,318 and 1,814 cannot be ordered in time.
• Coverage among private school and homeschooled children. The kindergarten survey does not reach them, so both the size of that population and its coverage are absent here.
• County-level shortfall inside individual states. A figure for Texas counties appeared in search results only and was not opened, so it is not carried here.
• Whether the change at ACIP reached any state list. The advisory committee shapes insurance coverage and the Vaccines for Children list. Whether any state altered a school entry requirement in response was not examined.
• What the 17 states outside the county study look like. Their absence is a limit of that design rather than an absence of data.
• Why any particular state exemption rate rose. No source opened here carries an on-the-record explanation from a state health department or a legislature for the increase in its own jurisdiction.
• What the November 2026 review will decide. One analysis judged 4 of 7 indicators already unmet and the remaining 3 unlikely to be met. That is an assessment, and no source opened here is the committee.

See the evidence

No federal statistical page was opened directly. The 2024-25 coverage and exemption figures come from an academic infectious disease policy center and a national hospital association reporting the CDC release of August 2025; the CDC pages carrying the underlying tables returned HTTP 403 to automated fetching and are listed here without a URL rather than dropped. The 2023-24 figures were read from the MMWR article mirrored at PubMed Central, which is the one federal statistical document opened directly, and the 1905 opinion in Jacobson v. Massachusetts was opened in a law school full-text repository of Supreme Court opinions as the only primary legal text. Where sources overlap they agree: the 92.5 percent figure for 2024-25 appears in two opened sources, and the 92.7 percent figure for 2023-24 is reproduced independently by subtracting the 7.3 percent documentation gap reported in the MMWR article. Where they disagree the disagreement is left visible rather than resolved — the 2025 national total is 2,288 in one opened source and 2,289 in another, with 2,144 and 2,231 appearing in search results that were not opened, and the two 2026 running totals of 2,318 and 1,814 come from articles that state no snapshot date. This is a research-based definition, so observation_refs is empty and provenance_mode: press-derived.

People affected

Estimated range 138,000–138,000 As of 2024-25

Sensitivity The interval has zero width and is not a confidence interval. Two corrections would move it in opposite directions and neither could be computed from the sources opened. Downward: an exemption from at least one required vaccine is not the same as lacking measles protection, because a child exempted only from varicella or DTaP may still hold two documented MMR doses, so this count overstates the measles-specific gap. Upward: about 280,000 kindergartners, or 7.3 percent, lacked documentation of two MMR doses in 2023-24, a larger and only partly overlapping count from the prior school year that includes children who were never exempted but arrived incompletely vaccinated or without records, and the 2024-25 update to that figure was not obtained here. Also upward: children in private schools and in homeschooling sit outside the kindergarten survey entirely, and neither their number nor their coverage was established in this round. The two counts are not nested in either direction, which is why the broader one is not used as an upper bound. The figure also measures paperwork filed at one grade in one year rather than the population at risk. Measles transmission is governed by coverage in the county and the school that a case actually reaches, and the only county-level evidence available covers 2,066 counties across 33 of the 50 states.

Regional breakdown The sources opened give state-level exemption rates and one national count of exempted children, but no state-level absolute count of exempted children. Deriving one would require state kindergarten enrollment figures that were not obtained, and splitting the national 138,000 by state population would be proportional allocation, which is wrong here because state exemption rates range from about 0.1 percent to 15.4 percent and therefore do not track population at all.