Could measles ever re-establish itself in the United States?

Yes, it is possible that measles could become endemic (constant presence of a disease in an area) in the United States again, especially if vaccine coverage levels in the United States decline.  This can happen when people forget to get vaccinated on time, don’t know that they need a vaccine dose (this is most common among adults), or refuse vaccines for religious, philosophical or personal reasons.

Research shows that people who refuse vaccines often group together in communities. When measles gets into communities with pockets of unvaccinated people, controlling its spread is very challenging while also increasing the likelihood of the virus re-establishing itself in the U.S. For a CDC description of a recent example of this epidemiologic phenomenon, go to:

High sustained measles vaccine coverage and rapid public health response are critical for preventing and controlling measles cases and outbreaks.