In Chinese Medicine there are two main ways to prevent getting the flu. The first is to boost your immune system. The second is to fend off any invaders before you get sick.
It is best to treat a disease before you get it by boosting your immune system. I recommend taking the mushroom reishi (Ganoderma, also called ling zhi) which will help boost your immunity and your energy.
But when the flu is going around, it is important to take an herbal formula which will help prevent the sickness. Gan Mao ling is a great formula for this. If you get the flu, this formula will not be powerful enough. At this point it is important to seek advice from a Chinese medicine doctor for the right formula.
People who get chronic colds will need a more customized herbal formula and acupuncture treatment.