Final answer:
Anaphylactic reactions to eggs or other allergens can occur before receiving the MMR vaccine. Epinephrine is used to counteract the effects of anaphylactic shock. Individuals with severe allergies should carry an epinephrine auto-injector.
Step-by-step explanation:
Anaphylactic reactions to eggs or other allergens can occur before receiving the MMR vaccine. Anaphylactic reactions are severe allergic reactions that can be life-threatening. They are typically caused by the release of histamine and other inflammatory chemicals from mast cells when an allergen is encountered. Epinephrine is often used to counteract the effects of anaphylactic shock. It is important for individuals with known severe allergies to carry an epinephrine auto-injector in case of exposure to an allergen.