Measles in South Carolina’s outbreak grew to nearly a thousand cases last week. The outbreak is part of a wave of measles outbreaks across the country that began last year in Texas. There are other outbreaks now in California, Utah and North Dakota. The vast majority of cases have been among unvaccinated people. The surge in cases is pushing the U.S. dangerously close to losing its measles-free status. Why are we losing the battle against measles?