If national coverage is 92.5 percent, is that close enough to be safe?

Not necessarily. The national average hides clustering. State coverage ranged from 78.5 to 98.2 percent, and within states there are pockets well below the roughly 95 percent threshold where protection holds. Safety depends on local coverage, not the national mean.

Is everyone who is unvaccinated a free-rider?

No. Infants under twelve months, the immunocompromised, and people facing access barriers cannot vaccinate and are exactly whom herd immunity is meant to protect. The free-rider logic describes voluntary deferral under high coverage, not the whole unvaccinated population.

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health · 2019 to 2026

Measles and the Last Five Percent

Herd immunity is a shared good that only holds above a threshold. A national average that looks fine can hide local pockets where the protection has already collapsed.

Facts verified as of June 2026.

US national MMR coverage among kindergartners was 95.2 percent in the 2019-2020 school year, the last endpoint at or above target [VERIFIED]. By the 2024-2025 school year it had fallen to 92.5 percent, leaving roughly 286,000 kindergartners without documented completion of the two-dose series [VERIFIED].

The national average hides the real epidemiology. In 2024-2025, state-level MMR coverage ranged from 78.5 percent in Idaho to 98.2 percent in Connecticut, and only about ten states reported coverage at or above 95 percent [VERIFIED]. Coverage is clustered, so many local communities sit well below threshold while the national number still looks close.

Sources

[VERIFIED] US kindergarten MMR coverage fell from 95.2 percent in 2019-2020 to 92.5 percent in 2024-2025, leaving about 286,000 undocumented. CDC SchoolVaxView, 2024-25 kindergarten vaccination coverage
[VERIFIED] 2024-2025 state MMR coverage ranged from 78.5 percent in Idaho to 98.2 percent in Connecticut; about ten states were at or above 95 percent. KFF analysis of CDC kindergarten data, measles elimination status
[VERIFIED] The US reported 2,288 confirmed measles cases in 2025, the most since 1992, and over 3,800 cumulatively through March 2026. KFF, citing CDC measles surveillance (2025-2026)
[VERIFIED] Measles R0 is conventionally cited as 12 to 18 in a fully susceptible population. Guerra et al., The basic reproduction number of measles: a systematic review, Lancet Infectious Diseases (2017)