Effect of antiviral treatment in older patients hospitalized with confirmed influenza

Seasonal influenza causes significant morbidity and mortality in people aged ≥65 years. Antiviral treatment can reduce complications and disease severity. The objective of this study was to investigate the effect of antiviral treatment in patients aged ≥65 years hospitalized with confirmed influenza in preventing intensive care unit (ICU) admission or death. A retrospective cohort study was carried out in 20 hospitals from seven Spanish regions during 2013-2015 in patients aged ≥65 years. Hospitalized cases of laboratory-confirmed influenza were selected. To assess the association between antiviral treatment and ICU admission or death, the adjusted odds ratios (aOR) and their 95% confidence intervals (CI) were calculated using multivariate logistic regression. We included 715 hospitalized patients, of whom 640 (87.9%) received antiviral treatment, 77 (10.8%) required ICU admission and 66 (9.2%) died. In the 64-74 years age group, receipt of antiviral treatment ≤48 h (aOR 0.20; 95% CI 0.04-0.89), 3-4 days (aOR 0.23; 95% CI 0.05-0.92) and 5-7 days (aOR 0.24; 95% CI 0.03-0.91) after clinical symptom onset was associated with reduced mortality. Receipt of treatment >7 days after symptom onset was not associated with reduced mortality. No association of antiviral treatment with reduced mortality was observed in the >74 years age group or with the prevention of ICU admission in any age group. Antiviral treatment had a protective effect in avoiding death in patients aged 65-74 years hospitalized due to influenza when administered ≤48 h after symptom onset and when no more than 7 days had elapsed.