A recently unveiled inquiry reveals a disconcerting trend: childhood inoculation rates for measles, mumps, and rubella have declined significantly in many American counties since the COVID-19 pandemic.
Disclosed within the pages of JAMA on June 2, the analysis combed through immunization statistics from county-level records accessible via state health department portals. Scholars at Johns Hopkins University meticulously traced kindergarten MMR vaccination data spanning pre-pandemic (2017–2018) and current (2023–2024) academic cycles. In cases where such granular data were scarce, approximated figures served as stand-ins.
Out of 2,066 counties surveyed across 33 states, an unsettling 78 percent reflected diminished inoculation figures. The average MMR coverage rate declined from a robust 94 percent pre-COVID to a concerning 91 percent, dipping below the herd immunity threshold of approximately 95 percent, as cautioned by epidemiological authorities.
Lauren Gardner, the principal architect of this study and helm of the Center for Systems Science and Engineering at Johns Hopkins, emphasized that the motive behind the work was to attain a “finer-grain, panoramic comprehension of the immunization terrain” across the US, according to Time.com.
Gardner remarked that while the CDC maintains state and national figures, the immunization tapestry weaves differently at community and sub-county strata. “When regions with lackluster coverage face a measles intrusion, they are much more susceptible to an outbreak. That’s precisely unfolding now,” she noted.
As of May 29, 1,088 measles infections have been officially reported across 33 jurisdictions, according to CDC data. A staggering 96 percent of those afflicted were either never vaccinated or had undocumented immunization status. In 2025 alone, there have been 14 outbreaks, culminating in three measles-related deaths—all involving unvaccinated individuals. Notably, the last such fatality prior to this year occurred back in 2015.
The MMR vaccine remains the frontline defense—proven both safe and powerfully effective. According to the CDC, most recipients achieve lasting protection after vaccination.
Among the 33 states analyzed, only four—California, Connecticut, Maine, and New York—showed an increase in median county immunization rates. The study did not delve into the roots of these discrepancies. However, Gardner posits that several dynamics—from pandemic-era healthcare disruption to differing societal attitudes and exemption laws—likely drive these divergences. Not coincidentally, these four states also uphold strict school vaccination mandates, disallowing non-medical opt-outs.
Hawaii, Gardner notes, showcased a dramatic regression. Once boasting a 95 percent vaccination shield pre-COVID, the state now languishes at 80 percent. Meanwhile, Wisconsin posted the lowest average rate in the study, hovering in the perilous 70 percent range, as per time.com.
Gardner warned that state-level averages often obscure hyperlocal vulnerabilities. “Drilling down further—say, school-by-school—might illuminate hidden pockets of risk. Only with that clarity can targeted efforts be deployed to elevate those numbers,” she affirmed.