The children are from Westmoreland county and are recovering at home. Officials are tracking every person the children may have been exposed to.
The two children had not been immunized. Children who have had vaccines are not at risk for contracting measles.
The Allegheny County Health Department, Pennsylvania Department of Health and Children's Hospital held a press conference top let parents know they should have their children immunized.
According to health department officials, 15 percent of all children in Allegheny County have not received all of the recommended vaccines. Vaccines in Pennsylvania are free for those under 18.
Measles is an acute, highly communicable rash illness transmitted by direct contact with infectious droplets. Less commonly it is spread airborne.