SIGH: Unvaccinated Behind Largest U.S. Measles Outbreak In Years. “The largest U.S. outbreak of measles to occur in 15 years — affecting 214 children so far — is likely driven by travelers returning from abroad and by too many unvaccinated U.S. children, according to new research. The finding could highlight the dangers of a trend among some U.S. parents to skip the measles-mumps-rubella (MMR) vaccine for their children, out of what many experts call misguided fears over its safety.” I blame Jenny McCarthy.