Influenza A (H1N1) 2009 Monovalent Vaccine Live, Intranasal is not approved for use in children <24 months of age. In a clinical trial with FluMist, among children 6-23 months of age, wheezing requiring bronchodilator therapy or with significant respiratory symptoms occurred in 5.9% of FluMist recipients compared to 3.8% of active control (injectable influenza vaccine made by Sanofi Pasteur Inc.) recipients (Relative Risk 1.5, 95% CI: 1.2, 2.1). Wheezing was not increased in children ≥24 months of age. Hypersensitivity, including anaphylactic reaction, has been reported during post-marketing experience with FluMist.