What is in measles vaccine and how is it delivered?

Measles virus: Measles vaccine is made from measles virus, but it's altered so that it causes no disease in most, but slight disease in a few (low grade fever and/or rash for 1-2 days). It is delivered via a needle into the tissue that lies under the skin. It stimulates the immune system to make antibodies against the virus, but without having to have the full-blown illness, with all the illness's risk, first.