Effect of neuraminidase inhibitor (oseltamivir) treatment on outcome of hospitalised influenza patients, surveillance data from 11 EU countries, 2010 to 2020

BACKGROUND: Timely treatment with neuraminidase inhibitors (NAI) can reduce severe outcomes in influenza patients. AIM: We assessed the impact of antiviral treatment on in-hospital deaths of laboratory-confirmed influenza patients in 11 European Union countries from 2010/11 to 2019/20. METHODS: Case-based surveillance data from hospitalised patients with known age, sex, outcome, ward, vaccination status, timing of antiviral treatment, and hospitalisation were obtained. A mixed effect logistic regression model using country as random intercept was applied to estimate the adjusted odds ratio (aOR) for in-hospital death in patients treated with NAIs vs not treated. RESULTS: Of 19,937 patients, 31% received NAIs within 48 hours of hospital admission. Older age (60–79 years aOR 3.0, 95% CI: 2.4–3.8; 80 years 8.3 (6.6–10.5)) and intensive care unit admission (3.8, 95% CI: 3.4–4.2) increased risk of dying, while early hospital admission after symptom onset decreased risk (aOR 0.91, 95% CI: 0.90–0.93). NAI treatment initiation within 48 hours and up to 7 days reduced risk of dying (0–48 hours aOR 0.51, 95% CI: 0.45–0.59; 3–4 days 0.59 (0.51–0.67); 5–7 days 0.64 (0.56–0.74)), in particular in patients 40 years and older (e.g. treatment within 48 hours: 40–59 years aOR 0.43, 95% CI: 0.28–0.66; 60–79 years 0.50 (0.39–0.63); ≥80 years 0.51 (0.42–0.63)). CONCLUSION: NAI treatment given within 48 hours and possibly up to 7 days after symptom onset reduced risk of in-hospital death. NAI treatment should be considered in older patients to prevent severe outcomes.