A peer-reviewed study from Boston Children's Hospital found that the U.S. has failed to meet 4 of 7 CDC criteria for maintaining measles elimination status, a designation held since 2000—with measles outbreaks spreading to 45 states since January 2025. Declining vaccination rates and continuous disease transmission for over a year triggered this reversal, putting infants and unvaccinated children at serious risk for complications. The Pan American Health Organization will formally reevaluate whether the U.S. loses its measles elimination status in November 2026, which would be a significant public health setback. (The FactCheck.org reference provided is from 2019 and addresses a different claim linking measles to immigration policy—not relevant to this post's factual content.)