A child who was not vaccinated has died from measles in West Texas. It's the first death in an outbreak that began late last month and the first from measles in the U.S. since 2015.

The effectiveness of the vaccine, coupled with rising vaccination rates, led to such low rates of measles that it was declared eliminated in the U.S. in 2000. In recent years, though, the virus has made a resurgence, as childhood vaccination rates have dropped nationwide.