ATLANTA, Ga. (WPVI) -- The CDC is reporting 704 cases of measles nationwide, as of Friday, April 26th - that's up 78 since last week.
The majority are in people who have not been vaccinated and half are under the age of 5.
Health officials in New York City have closed two schools for violating orders not to let any unvaccinated children to attend classes.
At two California universities, some students and faculty are released from quarantine.
However, hundreds remain in isolation until they can be cleared. They were put into quarantine after being exposed to the virus by a student who visited two busy libraries.
Government health officials are also working to dispel myths about the vaccine. They say is safe and effective.
They're also asking older Americans who remember measles outbreaks before the vaccine, and how devastating the disease can be, to encourage younger people to protect themselves.
One dose of the vaccine is 93-percent effective. Two doses is 97-percent effective.
The current recommendation for two doses was started in 1989. From 1963 until 1989, it was one dose. Many adults received a second dose later on, but not everyone.
If you're not sure, ask your doctor. Health care workers or those who travel overseas should make sure they've had a second dose, because you could be at a greater risk of being exposed.
If you were born before 1960, it's assumed you have been exposed and should be immune.
CDC: 704 measles cases nationwide, as cases mount