Asthma and respiratory allergies have not been identified as risk factor for severe Covid-19 disease in case series till now. This paper describes features that could be associated with this diminished risk. In 3 different asthma/allergy cohorts, it was examined whether ACE2 (the receptor for SARS-Cov-2 entry) expression on airway cells was reduced. Allergen sensitisation and allergen exposure was strongly associated with reduced ACE2 expression in all cohorts. This might be mediated by type 2 inflammation, as IL-13 reduced ACE2 in bronchial and nasal epithelium; non-atopic asthma was not associated with this reduction. The role of biological treatment for allergic or type 2 high asthma and SARS-Cov-2 susceptibility is yet unknown. The relation between type 2 inflammatory processes and SARS-Cov-2 disease severity could identify novel therapeutic strategies.

This article was selected by FJS van der Velden, MD (resident paeds) & G. Tramper, PhD, MD (paediatrician, paediatric infectiologist).