Answer:
A vaccine (or immunization) is a way to build your body's natural immunity to a disease before you get sick. This keeps you from getting and spreading the disease. For most vaccines, a weakened form of the disease germ is injected into your body.
Explanation:
What sets off appositives in the sentence is the use of the quotation mark, comma (,). This indicates that the phrase is just an added information in the sentence, and if omitted will never change the whole thought or idea of the sentence. Aside from commas, parentheses or dashes can be used as well.
