A nurse demonstrates how a measles vaccine is administered at the Orange County Health Department on May 6, 2019 in Orlando, Florida. According to the Centers for Disease Control and Prevention, the number of measles cases in the United States as of May 6, 2019 has climbed to 764 in 23 states, with 60 new cases reported in the past week, breaking recent records. (Photo by Paul Hennessy/NurPhoto via Getty Images)