Last week the anti-vaccination movement received a big legal blow. Federal Judge William Kuntz of Brooklyn ruled against three families who claimed that their religious rights were being violated when schools pulled their unvaccinated children out of class for fear of disease spreading through the school. Vaccinations have kept preventable childhood diseases, including measles and mumps at record lows in the last two decades. By 2000, measles was considered to have been essentially eradicated in the United States. The CDC has recently reported that the United States is experiencing a record number of measles cases this year with outbreaks spreading from New York to California. Daniel Salmon is Deputy director of the Institute for Vaccine Safety at the Johns Hopkins Bloomberg School of Public Health.