Answers: This is because the common cold is the result of a virsus and near is such a wide array of them which cause 'cold' symptoms that its impossible for doctors to dogmatic a single one or develope a vaccine to help your body argue them. The only root doctors are able to be paid a flu vaccine is because there are just three types of it. The common cold however could be the result of one of hundreds of virus.
Because nothing cures but the body. It take care of everything if it is given the hanging terrian to do it. It doesn't matter if its a drug or a supplement...nil cures...the body cures itself.