Systemic atopy and upper-airway disease define susceptibility to incident asthma after COVID-19 in Korea.

Incident asthma is an important respiratory sequela after COVID-19, but it is unclear which allergic phenotypes amplify risk. Using a linked nationwide Korean database of 3,987,182 individuals with confirmed severe acute respiratory syndrome coronavirus 2 infection, we compare claims-based incident asthma in those with pre-existing systemic atopy and/or upper-airway disease (allergic rhinitis, chronic rhinosinusitis, atopic dermatitis or food allergy) versus those without after 1:1 propensity score matching. During follow-up to 31 December 2022, participants with pre-existing disease have higher asthma incidence than matched controls (3.55 vs 2.13 per 1,000 person-years), with a hazard ratio of 1.66 (95% confidence interval 1.58-1.75). Asthma risk is elevated for each condition and increases with greater disease burden. These findings show that pre-existing allergic and upper-airway phenotypes stratify post-COVID incident asthma risk on a national scale, supporting targeted surveillance in high-risk subgroups.