Anyone with a severe (life-threatening) allergy to eggs.
Infants younger than 9 months of age
It may not be advisable if:
You are pregnant or breastfeeding
You have HIV/AIDS or another disease that affects the immune system.
Your immune system is weakened as a result of cancer or other medical conditions, an organ or bone marrow transplant, or radiation or drug treatment (such as steroids, cancer chemotherapy, or other drugs that affect immune cell function).
Your thymus has been removed or you have a thymus disorder, such as Myasthenia Gravis, DiGeorge syndrome, or Thymoma.