In 2000, following widespread vaccination, the U.S. eliminated measles, a highly contagious disease that can cause serious health complications. With elimination, measles no longer circulates regularly in the country, but outbreaks still occur when travelers are infected abroad and then encounter pockets of susceptible people. Most often, the travelers are unvaccinated and returning to the U.S.
The measles vaccine, which is administered in two doses as part of the measles, mumps and rubella, or MMR, vaccine, is safe and highly effective. To generate robust protection, the vaccine uses a live but weakened version of the measles virus. There’s no evidence that a vaccinated person has ever spread the weakened measles virus to another person.
Despite this, social media posts have incorrectly claimed or suggested that the ongoing measles outbreak in Texas is due to a vaccine strain and that vaccine clinics are the reason why the outbreak has grown.