This will be a two-year prospective study to characterize the nature of the remaining asthma exacerbations in patients treated with mepolizumab. Participants will be assessed every six months from pre- until two years of treatment in addition to whenever they experience an exacerbation of asthma during the study period. During these visits, various clinical, physiological and inflammatory outcomes will be assessed.

Before initiation of mepolizumab, a recording of patient's demographics, clinical, physiological and inflammatory features will be recorded. All subjects will be reassessed for the above measures at 6, 12, 18 and 24 months.

In addition to the above visits, patients will be assessed every time they experience either moderate or severe exacerbation of asthma over the treatment period.

Based on the percentage of sputum eosinophils and neutrophils, the type of inflammatory exacerbation will be determined

Inclusion Criteria:

• With a proven diagnosis of severe asthma as defined by the Canadian Thoracic Society
• Eligible for mepolizumab treatment
• Able and willing to sign the informed consent form

Exclusion Criteria:

• Any respiratory disease apart from asthma
• Confounding comorbidities sur as eosinophilic granulomatosis with polyangiitis (EGPA) or hypereosinophilic syndrome

Patients with severe asthma treated with mepolizumab at the IUCPQ-UL a tertiary care center from the Quebec city area.