The symbols do contain power, yes, but simply wearing a symbol will not offer you much protection unless you perform magic on it to make it act as a talisman.
Even then, it is all the more effective to clean your aura and keep a strong Aura of Protection going. These need to be done every day for true effectiveness in preventing diseases. Ever since I have been doing this consistently, I have not gotten the least bit sick once. It really works, but you have to stay on top of it and maintain your spiritual hygiene DAILY.