Introduction: Previous studies on the outcomes of asthma and COVID-19 have shown inconsistent results. This study aimed to elucidate the association between asthma and COVID-19 outcomes.
Methods: We conducted a prospective study with a large health plan to compare the incidence of COVID-19 infection, hospitalization and ICU admission in a cohort of 41,282 patients with asthma and a 1:1 age-, sex-, and race-ethnicity-matched cohort without asthma across the following pandemic periods: pre-Delta (03/01/2020 to 05/31/2021), Delta (06/01/2021 to 12/31/2021), and Omicron (01/01/2022 to 08/13/2022). Demographic factors, comorbidities, COVID-19 test results, inpatient utilization, and COVID-19 vaccination status were collected from electronic health records.
Results: Subjects with asthma were more likely than controls to undergo COVID-19 testing during the three pandemic periods and were less likely to test positive in the Omicron period (fully adjusted odds ratio=0.92; 95% CI=0.86– 0.98; p=0.01). Relative to controls, patients with asthma had an increased risk of hospitalization for COVID-19 (fully adjusted hazard ratio=1.33; 95% CI=1.08– 1.64; p=0.01) and borderline significant (p=0.05) higher rates of ICU admissions in the pre-delta period but not during the delta or Omicron periods. The increased risk of COVID-19 hospitalization associated with asthma was more pronounced in patients with severe asthma and in women compared with men. None of the associations were significantly modified by vaccination status.
Conclusion: Asthma was associated with a lower risk of COVID-19 infection but only during the Omicron period. Asthma was an independent risk factor for hospitalization for COVID-19 in the pre-delta period and this association was stronger for severe asthma and in women.
Keywords: asthma, COVID-19, severe asthma, cohort study