The number of children sickened by measles in 2019 was the highest in 23 years, according to new data published by the World Health Organization and the U.S. Centers for Disease Control and Prevention. In a study published on Thursday, WHO and CDC said there were nearly 870,000 cases of measles last year, and the number of deaths — about 207,500 — increased by almost 50% since 2016. Officials blamed the record number of cases on a significant drop in vaccination; children must receive two doses of the measles vaccine to avoid being sickened by the highly contagious disease.