Kindergarten shot records now name the exposed states: Idaho off 15 points, Maine up three

The national figure is small enough to mistake for noise: 2.6 percentage points of MMR coverage lost in ten years, from about 95 percent to 92.4 ^[1][3]. The variance underneath it is not small. Idaho's decade decline runs close to six times the national one ^[7], while Maine added 3.1 points and Connecticut 1.9 ^[4][5], and New York moved four tenths of a point ^[9]. Eighteen points separate the best and worst ten-year trends in the country ^[6]. A planning assumption drawn from the national average is wrong in both directions at once.

Composition matters more than the level. At 92.4 percent, 76 of every 1,000 kindergartners lack MMR, against roughly 50 a decade ago ^[2]. Nonmedical exemptions now stand at 4 percent of the age group ^[5], which is about 53 percent of that shortfall ^[3]. The exemption count covers at least one vaccine rather than MMR specifically, so treat that as the ceiling on the overlap and not the floor. Even at half, most of the gap is paperwork a parent filed on purpose. Scientific American attributes the post-2020 slide both to harder access during the pandemic and to a wave of vaccine skepticism ^[18]; only the first of those is fixable by opening a clinic on a Saturday.

The reason a few points matter here is the attack rate. Adam Ratner of NYU calls measles the most contagious disease known, ahead of flu, COVID, polio and Ebola ^[12], and roughly 90 percent of unvaccinated people exposed to it become infected ^[13]. Run that against current coverage and a fully exposed cohort of 1,000 kindergartners produces about 68 infections ^[10]. Coverage for polio, hepatitis B and DTaP has fallen on a similar track ^[4], but those pathogens do not convert exposure into cases at that rate.

Geographic predictability has a resolution limit, and Virginia is where it shows. Its share of this year's national case count is around 7 percent ^[9] despite above-average coverage, because pockets of unvaccinated people can sustain transmission even where the statewide number looks comfortable ^[17]. A ranked table tells a state health officer which states to staff for. It does not tell a superintendent whether their district is one of the pockets.

On policy, Lori Handy of the Vaccine Education Center at Children's Hospital of Philadelphia says states that bar personal exemptions run higher coverage ^[14]. About two thirds of states already bar them, and only four bar religious exemptions as well ^[15], which leaves 46 states with a non-medical route still open ^[8]. Most states already require MMR for public school enrollment ^[19]. The requirement is not the variable. The exit from it is.