http://www.cdc.gov/media/releases/20...9-measles.html
The CDC is also saying that the number of children who have been cleared to not be vaccinated and still attend school has surpassed 8%. They believe that mark is when school environments lose herd immunity, and those with compromised immune systems become vulnerable.“The current increase in measles cases is being driven by unvaccinated people, primarily U.S. residents, who got measles in other countries, brought the virus back to the United States and spread to others in communities where many people are not vaccinated,” said Dr. Anne Schuchat, assistant surgeon general and director of CDC’s National Center for Immunizations and Respiratory Diseases. “Many of the clusters in the U.S. began following travel to the Philippines where a large outbreak has been occurring since October 2013.”