Increased Risk of New-Onset Asthma After COVID-19: A Nationwide Population-Based Cohort Study

Background: Previous studies have suggested that respiratory virus infections may be associated with new-onset asthma. However, whether coronavirus disease 2019 (COVID-19) is associated with an increased risk of new-onset asthma remains unclear. Objective: We aimed to evaluate whether recent COVID-19 increases the risk of new-onset asthma and whether COVID-19 vaccination could mitigate this risk. Methods: We constructed 3 different study designs using the Korean National Health Insurance claim-based database: study 1: COVID-19–diagnosed subjects (COVID-19 cohort) and their matched controls; study 2: COVID-19–vaccinated subjects (vaccination cohort) and their matched controls; and study 3: vaccination cohort and their matched controls, excluding subjects diagnosed with COVID-19. Results: In study 1, 1.6% of the COVID-19 cohort and 0.7% of the matched cohort developed new-onset asthma, with incidences of 31.28 and 14.55 per 1,000 person-years, respectively (P <.001). The COVID-19 cohort had a higher risk of new-onset asthma (adjusted hazard ratio [aHR] 2.14; 95% CI 1.88–2.45) than matched controls. In study 2, the vaccination cohort had a lower risk of new-onset asthma than the matched controls (aHR 0.82; 95% CI 0.76–0.89). However, among subjects without a COVID-19 diagnosis, COVID-19 vaccination was not associated with a reduced risk of new-onset asthma in study 3 (aHR 0.95; 95% CI 0.87–1.04). In subgroup analysis, the risk of new-onset asthma was significantly lower in fully vaccinated subjects and higher in older subjects and in those with diabetes mellitus than in their counterparts. Conclusions: The COVID-19 was associated with a higher incidence of new-onset asthma, which might be preventable by COVID-19 vaccination.