Data source

We defined a cohort of asthma patients initiating treatment with omalizumab between 2010 and 2016, using claims data from the Belgian national social security department [11]. These claims data encompass drug dispensing, medical services, hospitalisation and related costs. Information on dispensing included the following: brand and generic name, strength, defined daily dose (DDD), dispensing date and Anatomical Therapeutic Chemical (ATC) classification code [12, 13]. Information on indication of use and underlying comorbidity was not available. In Belgium, affiliation with a social health insurance provider is mandatory, implicating that we have data on all Belgian residents [11].