Literature Search

The literature search in PubMed resulted in 13 publications (14–26). For key characteristics of the studies see Tables S1 (grass pollen studies), S2 (tree pollen studies), S3 (house dust mite (HDM) studies) and S4 (studies not differentiating between allergens) in supplementary information. Some analyses were funded by manufacturers of AIT preparations like the ReWARD (Real World Evidence in Allergy Research and Development) program by Allergopharma GmbH & Co. KG, Germany (14,15,17), the BREATH (Bringing Real-World Evidence to Allergy Treatment for Health) program by Stallergenes Greer, France (18,19,21,22) with Devillier et al. 2017 (22) representing a subanalysis of Zielen et al. (21) and the REACT (Real world effectiveness in allergy immunotherapy) study by ALK-Abelló, Denmark (25). ALK-Abelló, Denmark supported two further studies (16,26). Additionally, there are three publications focussing on medication adherence; one each initiated by ALK-Abelló (20) and Stallergenes Greer (23), while no company funding is mentioned in the third one (24).
The analyses were carried out using retrospective prescription databases from
The data mostly include demographic information (sex and age) and information related to prescriptions, e.g. product, pack size, pack count and prescriber. Diagnoses according to the International Statistical Classification of Diseases and Related Health Problems-10 (ICD-10) codes were available in three studies (16,25,26).
Each of the studies listed has defined exclusive inclusion and exclusion criteria, which may be found in the respective original publications.
The 13 publications presented data on effectiveness and/or medication adherence for AIT in general, preparation groups or single SCIT and SLIT products. Some of the assessments focused on certain allergens (grass pollen, tree pollen, house dust mites), while others did not.
Most of the assessments investigating effectiveness of AIT consistently predefined different time intervals before (pre-index period), during (treatment period) and after AIT application (follow-up period) (15,17–19,21,22). In other assessments, the whole period after receiving the first AIT prescription was designated as follow-up period (16,25,26).
Effectiveness of AIT was calculated by comparison to a Non-AIT control group receiving prescriptions of symptomatic medication for the treatment of AR and/or anti-asthmatic medication for the treatment of asthma.
Non-AIT control patients were matched with patients receiving AIT in order to minimize confounding bias. An ‘exact matching’ method was conducted in 6 studies (15,17–19,21,22) on the basis of several variables, e.g. age class, sex and asthma status. In one analysis ‘propensity score matching’ was performed (25).
In this overview, we focus on data concerning the long-term effectiveness of AIT, i.e. during the full analysis period (treatment plus follow-up period) and follow-up periods as well as medication adherence.
1) Long-term effectiveness of AIT was evaluated by means of the following endpoints:
2) Medication adherence to AIT was evaluated based on different definitions: adherence, compliance, persistence and/or days on therapy.