Eosinophilia in Asthma Patients Is Protective Against Severe COVID-19 Illness

There is a paucity of information on coronavirus disease 2019 (COVID-19) outcomes in asthmatics.

To identify risk factors associated with admission and subsequent mortality among COVID-19-infected asthmatics.

Adults at our institution with a positive polymerase chain reaction for COVID-19 between March 14 and April 27, 2020, were retrospectively identified. Comorbidities, laboratory results, and mortality rates during hospitalization were recorded.

In total, 737 of 951 (77.5%) asthma patients with COVID-19 were seen in the emergency department (ED), and 78.8% of these ED patients (581 of 737) were admitted. Individuals with previously measured mean absolute eosinophil counts (AEC) ≥150 cells/μL were less likely to be admitted (odds ratio [OR] = 0.46, 95% confidence interval [CI]: 0.21-0.98, P = .04), whereas concomitant heart failure (CHF), chronic kidney disease (CKD), and chronic obstructive pulmonary disease (COPD) were risk factors for admission. Hospitalized patients with asthma with peak hospital-measured AEC ≥150 cells/μL (n = 104) were less likely to die compared with those whose AEC remained <150 cells/μL (n = 213) (mortality rate 9.6% vs 25.8%; OR = 0.006, 95% CI: 0.0001-0.64, P = .03). This group had also higher preadmission mean AEC (237 ± 181 vs 163 ± 147 cells/μL, P = .001, OR = 2012, 95% CI: 27.3-14,816). The mortality rate in patients with asthma alone (no associated CHF, CKD, COPD, diabetes, or hypertension) was similar to that of patients without asthma or any of these comorbidities.

In asthmatics, pre-existing eosinophilia (AEC ≥150 cells/μL) was protective from COVID-19-associated admission, and development of eosinophilia (AEC ≥150 cells/μL) during hospitalization was associated with decreased mortality. Preadmission AEC influenced the AEC trend during hospitalization. Having a Th2-asthma phenotype might be an important predictor for reduced COVID-19 morbidity and mortality that should be further explored in prospective and mechanistic studies.