Industrial vitamins didn't help me. These days, whenever I start coughing or having runny nose, you know what I do? Get out for an hour, just walking around the neighborhood. Properly dressed of course (knit, cap, scarf, gloves, winter jacket, pants and boots). Helps a lot. Also using homemade remedy for prevention. Ginger honey lemon tonic. It taste a bit vile, because of ginger but it helps, even if its just placebo. Which I don't believe is the case, because ingredients have widely known heath benefits. For example, during flu season I experienced really nasty cough which eventually forced me to vomit. Used syrup but it didn't help at all, just like antibiotics. One teaspoon of honey stopped the cough and nausea instantly. Couldn't sleep without it.