Ethnic differences in the incidence of clinically diagnosed influenza: an England population-based cohort study 2008-2018

ABSTRACT We used primary and linked secondary healthcare data to investigate the incidence of clinically diagnosed influenza/influenza-like-illness (ILI) by ethnicity in England from 2008-2018. We identified higher incidence rate ratios for influenza/ILI among South Asian (1.70, 95% CI 1.66-1.75), Black (1.48, 1.44-1.53) and Mixed (1.22, 1.15-1.30) groups compared to White ethnicity. People from ethnic minority backgrounds are represented disproportionately among patients with severe COVID-19. Recent research has found people of Black and South Asian ethnicity have increased risk of SARS-CoV-2 infection, COVID-19-related hospitalization and death, independent of deprivation, occupation, household size, and underlying health conditions(1,2). The COVID-19 pandemic has reinforced the importance of seasonal influenza vaccination. By preventing influenza-related hospitalization, vaccination can minimize the risk of hospital-acquired COVID-19 (co-) infection for these individuals and reduce health service pressures, particularly the need for isolation of patients with respiratory symptoms awaiting COVID-19 test results. In the UK, influenza vaccine is routinely recommended for adults aged ≥65 years, or people <65 years with underlying health conditions. These recommendations formed the basis of the original guidance to identify patients at moderate- and high-risk of COVID-19. Influenza vaccine recommendations were expanded for the 2020/21 season to include all adults ≥50 years(3). However, vaccine uptake among clinical risk groups is low, particularly for Black and Mixed Black ethnic groups(4). In addition, people of non-White ethnicity have higher risk of severe outcomes following influenza infection(5,6). It is unclear whether this is driven by the risk of infection or complications, with most research focused on distal outcomes rather than initial infection risk. Here we investigate the incidence of influenza and influenza-like-illness (ILI) by ethnicity from 2008-2018 among people not eligible for routine influenza vaccination, to consider disparities in infection risk.