Allergen-specific immunotherapy and COVID-19: What happened?

Background: The COVID-19 infection played a key role in the discontinuation of patient treatment, such as allergen-specific immunotherapy, in chronic diseases. Objectives: We conducted a retrospective observational study at Verona University Hospital, Verona, Italy, to assess the level of adherence to sublingual immunotherapy (SLIT) in patients affected by allergic rhinitis and mild asthma. Materials and methods: We compared and analysed data related to first prescription and collection of 5-grass-pollen 300-index of reactivity (IR) SLIT and tablet lyophilisate, containing 75,000 standardized quality tablet units (SQ-T) allergen extract of grass-pollen from Phleum pratense L, for the five-year period 2017-2021.In particular we considered the group of naïve patients from 2017 who completed pre-COVID treatment (2017-2019) and the group of naïve patients from 2019 who completed treatment during the COVID period (2019-2021). The significance test used was Student's t-test, and P ˂ 0.05 was considered as statistically significant. Results: In the three-year period 2017-2019, 264 naïve patients began treatment in 2017, of these 181 continued in 2018, 135 continued in 2019. Instead, for the period 2017-2019, there were 226 naïve patients in 2019; of these 139 continued in 2020, and 102 in 2021. Conclusions: COVID-19 did not seem to influence adherence to SLIT, which declined independently even in during the pre-pandemic 3-year period.