Study design
This study was a retrospective data analysis using a German longitudinal prescription database (LRx, IQVIA, Frankfurt am Main, Germany). The overall analysis period was January 2008 to June 2020 (see Figure 1).
The index period for the study was defined from September 2009 to August 2013, including four allergy seasons (September to August). For the AIT group, eligible patients were initiated on the respective SCIT products at index date during this period. A pre-index period of 12 months before SCIT initiation was determined. Treatment period lasted from index date until expiry of the last prescription of the respective product followed by the follow-up period of at least two years until end of the study in June 2020.
For the control group, index date was defined as the first prescription in the second allergy season during the index period. Treatment period was from index date until expiry of the last prescription of the respective product within a maximum of five years followed by the follow-up period of at least two years until end of the study in June 2020.
Three authorized allergoids in Germany containing grass or tree pollen were analysed: one MCT®-associated allergoid and two aluminium hydroxide adjuvanted allergoids (allergoid 2 and 3, respectively). For the control group symptomatic AR medications were defined in accordance with the ARIA guideline 2019 .