The other 2 arteries that bring blood to the brain, called the vertebral arteries, supply the brainstem. Plaque in the vertebral arteries is much less likely to break off and cause a stroke, but narrowing in the vertebral arteries can cause problems if the brainstem does not get enough blood flow.
A child should receive the first shot when he is between 12-15 months, and the second when he's between 4-6 years of age. If you're not sure if you have had the diseases or the vaccines (prior to 1971 it was given in three separate shots), you can get the MMR vaccine as an adult.
WHENFor children, the first dose should be given at 12 through 23 months of age. Children who are not vaccinated by 2 years of age can be vaccinated at later visits. For others at risk, the hepatitis A vaccine series may be started whenever a person wishes to be protected or is at risk of infection.