A Study of Xolair to Evaluate Effectiveness and Long-Term Safety in Patients With Moderate to Severe Asthma

Inclusion Criteria: * Signed informed consent document (in the case of a minor, consent must be given by the child's parent or legally authorized representative) * ≥12 years of age * Physician diagnosis of moderate to severe persistent asthma * Evidence or history of positive skin test or in vitro reactivity to an aeroallergen * Willingness to participate fully for the duration of the study (5 years) * For patients in the Xolair-treated cohort, have received at least one dose of Xolair therapy at the time of enrollment Exclusion Criteria: * Contraindication to Xolair therapy (e.g., patients who experienced a severe hypersensitivity reaction to Xolair) * Acute asthma exacerbation within the previous 2 weeks of screening requiring any of the following: initiation of systemic corticosteroids, increased doses of systemic corticosteroids from baseline, doubling of inhaled corticosteroids, emergency room visit, or hospitalization * Acute flare of significant systemic disease (e.g., infection, hematologic, renal, hepatic, cardiovascular diseases, or gastrointestinal diseases), or a recent hospitalization because of their disease within the previous 2 months * Use of an experimental drug within 30 days prior to study screening * Diagnosis of cystic fibrosis * For patients in the non-Xolair-treated cohort, any prior treatment with Xolair