The clinical predictors of and vaccine protection against severe influenza infection in children.

Influenza infection in children causes a tremendous global burden. In this study, we aimed to investigate the clinical predictors of severe influenza among children. We retrospectively included hospitalized children who had laboratory-confirmed influenza infection and were admitted to a medical center in Taiwan between 2010 and 2018. Severe influenza infection was defined as needing intensive care. We compared demographics, comorbidities, vaccine status and outcomes between patients with severe and nonsevere infection. There were 1030 children hospitalized for influenza infection: 162 patients needed intensive care and 868 patients did not. Multivariable analysis revealed that an age below 2 years (adjusted odds ratio [aOR] 3.31, 95% confidence interval [CI] 2.22-4.95), underlying cardiovascular disease (aOR 1.84, 95% CI 1.04-3.25), neuropsychological (aOR 4.09, 95% CI 2.59-6.45) or respiratory disease (aOR 3.87, 95% CI 1.42-10.60), patchy infiltrates (aOR 2.52, 95% CI 1.29-4.93), pleural effusion (aOR 6.56, 95% CI 1.66-25.91), and invasive bacterial coinfection (aOR 21.89, 95% CI 2.19-218.77) were significant clinical predictors of severe disease, whereas severe infection was less likely in individuals who had received influenza and pneumococcal conjugate vaccines (PCVs) (aOR 0.51, 95% CI 0.28-0.91; aOR 0.35, 95% CI 0.23-0.51, respectively). The most significant risk factors associated with severe influenza infection were an age under 2 years, comorbidities (cardiovascular, neuropsychological, and respiratory diseases), patchy infiltrates or effusion shown on chest X-rays, and bacterial coinfections. The incidence rate of severe disease was significantly lower in those who had received influenza vaccines and PCVs.