On Jun. 17, 2003, the U.S. Food and Drug Administration (FDA) announced it had approved FluMist. This was the first nasally administered vaccine in the US which consists of live virus vaccine including 2 strains of influenza A at one strain type B.

The drug was tested in 20,228 subjects including at least 10,000 healthy children 5 to 17 years. Efficacy was approximately 87% in children; for healthy adults, aged 18–49 years, the vaccine also reduced severe illness. The drug approved for prevention of influenza A and B in healthy persons age 5 to 49 years. For children 5 to 8 years, there will need to be 2 doses separated by at least 6 weeks; for those 9 to 49 years only a single dose is recommended.

This is a live virus vaccine that should not be used in those with HIV or other immune deficiencies. Another concern is storage-the current product must be stored at −15°C. Anticipated problems are product stability and freezer space. The initial plan for availability without prescription in pharmacies in states that have approved this delivery mechanism. The FDA has warned that the safety of FluMist in patients with asthma has not been established. It should also not be used in persons >50 years those with chronic medical conditions and those with immune deficiencies.