Protective Effect of Antiviral Treatment of Hospitalised Influenza Patients on the Risk of Death, EU 2010-2020

Background: Research indicates that timely treatment with neuraminidase inhibitors (NAI) reduces severe outcomes in influenza-infected patients. Our aim was to analyse case-based data on NAI treatment in hospitalised laboratory-confirmed influenza patients in EU countries from 2010/11 to 2019/20 to assess this.Methods: Propensity weighted adjusted robust Poisson regression models were used to estimate the incidence rate ratio (IRR) for in-hospital death in patients treated with NAIs versus not treated, adjusted for age, sex, virus (sub)type, timing of hospitalisation and treatment, hospital unit, and spatial clusteringFindings: NAI were mostly (83%) given within two days after hospital admission. Our results support the role of early treatment within 48 hours (incidence risk ration (IRR) 0·63; 95% confidence interval (CI) 0·56-0·70), even administered later than 48 hours and up to seven days, to reduce the risk of in-hospital death. Older age and intensive care unit admission (IRR 2·69; 95%CI 2·49-2·91) increased the risk of dying, while early hospital admission after onset of symptoms decreased the risk (IRR 0·94; 95%CI 0·92-0·95). Age-stratified analysis showed that NAI treatment reduced the risk in people 40 years and older. Among hospitalised patients with underlying conditions and clinical complications, antiviral treatment reduced risk to die when given within 48 hours after onset of symptoms compared to later (IRR 0·79; 95%CI 0·66-0·94).Interpretation: NAI treatment given up to seven days after symptom onset reduced the risk of in-hospital death. NAI treatment should be considered particularly in age-group ≥ 40 to prevent severe outcomes.Funding Information: Internal funds of ECDC. Declaration of Interests: None declared.Ethics Approval Statement: Not required.