After the MMR and Chickenpox (Varicella) vaccines, your child may break out in a rash 10-20 days after the immunization. The MMR rash is not contagious, and it doesn't hurt or itch. It will go away on its own. The chickenpox rash can be very contagious in very few cases. Try to keep your child away from anyone with a compromised immune system (such as cancer, HIV or on Corticosteroids or other medicines that affect the immune system). If the spots are where the shot was given, place a band-aid over them. This will help prevent spread of the chickenpox.