The FDA has ruled that FluMist, a nasal spray flu vaccine from MedImmune, is safe for children under 5.

FluMist is currently indicated for healthy children and adolescents 5 to 17 years of age and healthy adults 18 to 49 years of age.

Previous research showed that FluMist was associated with negative side effects in children under 12 months old, as well as in children between 12 months and 5 years with a history of wheezing.

Monday, the FDA posted new documents on its Web site stating that studies show the vaccine apparently prevents influenza in children as young as six months. The FDA also noted that children taking FluMist were more likely to develop wheezing problems when compared to children treated with an injectable vaccine.

One of the studies reviewed by the federal agency showed that approximately 3 percent of children 6 months to 1 year old who took FluMist were hospitalized for respiratory problems, while only 1 percent of children that age who took the injected vaccine experienced the same difficulties.

The respiratory problems were not fatal in any of the cases. At the FDA’s request, a panel of outside experts will analyze whether the side effects warrant limiting the vaccine's use in young children.

Scientists have argued that MedImmune’s nasal spray flu vaccine is more effective than injection, due to the fact that it stimulates immunity in the nose first, and then the rest of the body. Vaccine injections, which use dead viruses, do not stimulate extra reaction in the nose.

Unlike vaccine injections, which use dead viruses, FluMist contains a live and weakened virus. The spray was first licensed in the United States in 2003. Its supporters argue that, when sprayed into the nose, antibodies develop there (the flu virus is transmitted in the air and is often inhaled through the nose.)

Experts say vaccination is the best prevention strategy there is, followed by thorough hygiene (washing hands, covering your mouth when you cough, keeping away from public spaces when sick etc).

According to the Centers for Disease Control and Prevention, an average 5% to 20% of US residents get the flu each year; of these, more than 200,000 people are hospitalized from flu complications. Approximately 36,000 people die from flu.

Younger children and the elderly are at particular high risk for complications from the flu, the CDC says.