Both the seasonal and the H1N1 vaccines come in two varieties an injectable form and a nasal spray, FluMist. Ideally, anyone needing two doses of either the seasonal or the H1N1 vaccine should stick to the same form of inoculation the shot or the spray.
But if that's not possible, it's O.K. to mix and match. Children younger than 10, for example who need two doses of the 2009 H1N1 vaccine can get one FluMist and one injectable dose.
Only one combination is not recommended. If you need to get the seasonal and 2009 H1N1 vaccines at the same time, don't get FluMist for both. "It's a question of how the immune system deals with a live virus," says Dr. Anne Schuchat, director of the CDC's National Center for Immunization and Respiratory Diseases. "It's better not to push two live-virus vaccines at the same time."
Again, pregnant women, anyone under 2 or over 49 and those with an underlying condition like heart disease, asthma or a compromised immune system should not get the spray vaccine. But the injectable version, made from the killed influenza virus, is approved for everyone 6 months old and up.