More measles cases have been reported in 2018 than 2017, Centers for Disease Control and Prevention said.
The CDC said most of the people who became sick weren't properly vaccinated.
One dose is 93 percent effective at fighting the measles if someone around you has the virus, and
two doses is 97-percent effective, the CDC said.
For people that have had measles, but got the shot have milder cases and are less likely to spread it.
However, many people are still against the vaccine, despite its proven effects.