From the FluMist article on Snopes [[Status: Undetermined):
... Flu shots are made from killed flu viruses and are suitable for anyone 6 months or older. FluMist is made from a weakened live virus, so it isn't deemed safe for people with chronic medical problems or weak immune systems. For this reason, the Food and Drug Administration [[FDA) approved FluMist only for healthy 2- to 49-year-olds. Those under two years of age or over forty-nine must continue to make do with the injected vaccine, as must those who have other health problems.

But even for the healthy 2- to 49-year-olds, the spray vaccine poses a risk, if not to them, then to those they come into contact with. In a few rare instances, those who receive this live vaccine will as a consequence spread it to others, so FluMist isn't recommended for people who take care of those with severely compromised immune systems who are being tended in protective environments. However, the CDC says: "People who have contact with others with lesser degrees of immunosuppression [[for example, people with diabetes, people with asthma taking corticosteroids, or people infected with HIV) can get LAIV [[FluMist)."

The live virus can be transmitted to others by way of coughing, sneezing, or talking, or via a fomite, an item touched by someone who has the virus. [[Common cold, flu, and stomach viruses can live on the fingertips for hours, and they can survive on the surfaces of objects for days.) However, says the CDC: "Because the viruses are weakened, infection is unlikely to result in influenza illness symptoms since the vaccine viruses have not been shown to mutate into typical or naturally occurring influenza viruses.