Some people are a firm believer of multivitamins; and I am one of them. Well, I don't actually practice what I preach (since sometimes I forget to take my vitamins myself, lol), but I always make sure that my kids take theirs everyday. Nothing complicated; just a daily dose of vitamin C and a multivitamin. I believe that it does help us strengthen our immune system, and even help us save money from buying all those expensive medical treatments.
But it's your choice ... :)