Hi, IgG stands for immunoglobulin G, this is a special type of protein that works as our immune system against germs. When it is deficient we are at risk of contracting infections. So we need to be careful about this. It can be given as an infusion or subcutaneous infusion. Subcutaneous infusion drug is given just below the details of skin. The skin is raised and the very small needle just passes the skin and the drug is given this is how we give insulin. Yes, you may be given the vaccine, many of which are given subcutaneously and mighty be similar to that while you went for overseas. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Mahboob Ur Rahman, General & Family Physician