I take thymic synergy by Metagenics...it has Vitamins a,c, b6, b5, calcium phosphorus, zinc, selenium, copper, molybdenum, as well as citrus bioflavanoid complex, raw thymus, raw spleen, and raw adrenal concentrates. In addition I take a few other things with extra zinc, which helps with the immune system. Vitamin A and zinc are overlooked often in their function of immune system support. Taking vitamin C alone is not enough.