Question from Anita at ovolina.com: My doctor suggested I get a vaccine even if already exposed to H1N1 with five sick kids but I'm not sure what to do.     

Dr. Natterson:  The question you sent is actually fairly common. Most doctors (myself included) recommend the H1N1 vaccine even if a person has had influenza already this year. The reason is that most people who had “flu” did not have documented flu with a positive test. So many people think they have built up immunity when they have not. Even among those who did have true flu—those who went to the doctor and had a test that came back positive for influenza A—almost none of them (except folks whose samples went to CDC or investigative labs early on) knows what strain of flu they had. So, it is possible that the strain of H1N1 protected with the vaccine is different than the strain they had. For people in this second group, if they are exposed to a different strain of H1N1 this winter they could potentially get the flu again; by vaccinating the risk of infection is reduced.

Dr. Cara Natterson, a graduate of Harvard University and the Johns Hopkins School of Medicine, is a respected pediatrician and the author of "Dangerous or Safe? Which Foods, Medicines and Chemicals Really Put Your Kids at Risk (Oct 2009), "Your Newborn: Head to Toe", "Your Toddler: Head to Toe" - comprehensive medical resource guides for parents.