0 notes April 29, 2009 For the this flu season herbs like Andrographis paniculata, Olive leaf Extract, Oregano Oil, Zinc, Elderberry, and Garlic could be a good way to build a resistant immune system. Of course Vitamin C is very important as well, but make sure that the Vit C is GMP certified as their has been lead and mercury contamination on cheap brands of Vit C coming from China. Also Vit C is not as effective with out Biflavanoids.