Outcomes and Risk Factors with COVID-19 or Influenza in Hospitalized Asthma Patients

Background: At the time of the SARS-CoV-2 emergence, asthma patients were initially considered vulnerable because respiratory viruses, especially influenza, are associated with asthma exacerbations, increased risk of hospitalization and more severe disease course. We aimed to compare the asthma prevalence in patients hospitalized for COVID-19 or influenza and risk factors associated with poor prognosis with the diseases.

Methods: This retrospective cohort study used the Paris university hospitals clinical data warehouse to identify adults hospitalized for COVID-19 (January to June 2020) or influenza (November 2017 to March 2018 for the 2017-2018 influenza period and November 2018 to March 2019 for the 2018-2019 period). Asthma patients were identified with J45 and J46 ICD-10 codes. Poor outcomes were defined as admission in intensive care or death.

Results: Asthma prevalence was significantly higher among influenza than COVID-19 patients (n = 283/3 119, 9.1%, 95% CI [8.1-10.1] in 2017-2018 and n = 309/3 266, 9.5%, 95% CI [8.5-10.5] in 2018-2019 versus n = 402/9 009, 4.5%, 95% CI [4.0-4.9]). For asthma patients, 31% with COVID-19 were admitted to an intensive care unit versus 23% and 21% with influenza. Obesity was a risk factor for the 2017-2018 influenza period, smoking and heart failure for the 2018-2019 period. Among COVID-19 patients with asthma, smoking and obesity were risk factors for the severe form.

Conclusions: In this study, patients with an asthma ICD-10 code were less represented among COVID-19 patients than among influenza-infected ones. However, outcomes were poorer for COVID-19 than influenza patients, both with asthma. These data highlight the importance of protective shields and vaccination against influenza and COVID-19 in this population.