The measles vaccine stimulates the body's immune response and is considered highly effective.
Toddlers in the D.C. region are well-vaccinated according to the Center for Disease Control, but there is room for improvement.
Dr. Jane Seward with the CDC says this year there's been a record number of measles cases in the country.
"We usually get 60 a year. This year we've had 600," she says.
Earlier this year, a young girl from Northern Virginia came home after contracting the disease overseas. Only one other person was infected, but Seward says many toddlers in the state aren't getting vaccinated on time.
"About one child in eight is not getting their MMR vaccine on time," she says.
The CDC's annual report card found children in Maryland and D.C. aged 19-35 months are more likely to be vaccinated on time than in other parts of the U.S. Virginia ranked average.