Association between peripheral blood eosinophils count and mortality in respiratory infections

<bold>Introduction:</bold> Patients with Type 2 high asthma may experience a reduced risk of severe clinical outcomes associated with COVID-19. However, it remains unclear whether these findings are attributed to Type 2 inflammation or the antiviral and antibacterial immunity associated with eosinophils. <bold>Aim:</bold> To examine pre-existing absolute eosinophilic count (AEC) as a prognostic marker for mortality in bacterial pneumonia and in respiratory infections due to SARS-CoV-2, influenza <bold>Methods:</bold> We used the computerized database of Clalit Health Services, the largest health care provider in Israel, to identify all adult patients who underwent PCR testing for SARS-CoV-2, hospitalized patients due to influenza confirmed by PCR or bacterial pneumonia. A cohort approach was used to assess the association between AEC ≥ 150 or <150 cells/μl and 30-day mortality. <bold>Results:</bold> 77100 patients with COVID-19,47174 with bacterial pneumonia and 7810 patients with Influenza included in the study. Pre-existing AEC ≥ 150 in patients infected with COVID-19, both asthmatics and non-asthmatic was associated with significant reduced risk for moderate to severe disease. Pre-existing AEC ≥ 150 was associated with significantly reduced risk of mortality in patients hospitalized with Influenza or bacterial pneumonia (HR, 0.67 (0.53-0.84), HR 0.79 (0.75-0.83) respectively ,with only a tendency to reduced mortality in COVID-19 HR0.92 (0.84-1.02). <bold>Conclusion:</bold> Preexisting high eosinophil blood levels are associated with decreased mortality in viral and bacterial infection in the general population. This may due to eosinophils protective role in viral or bacterial respiratory infections.