The percentage of children who have not received all of their required vaccines prior to entering kindergarten varies by state, but Maine is tied for ninth place for the highest opt-out rate in the nation. Public health professionals worry that, because parents are choosing not to vaccinate their children, diseases like measles and whooping cough will come back. The map of Maine shows the rate by county in 2012 that children aged 19-35 months received all the vaccinations that were due by the time they were 18 months old. Related story