Hospitalization cost estimates of respiratory syncytial virus and influenza infections in adults in Spain, 2016–2019

Respiratory syncytial virus (RSV) is increasingly a recognized cause of severe respiratory infection among adults. This retrospective observational study compared the costs of RSV and influenza hospitalizations in adults aged ≥18 years admitted to the Spanish National Healthcare System between 2016 and 2019. Mean costs per hospitalization episode were compared using a multivariable log-gamma generalized linear model adjusted by age, risk group and calendar year. Total annual hospitalization costs were estimated from population incidence rates (for RSV we used model-based rates reported in a published study due to the substantial under-ascertainment of cases) and the mean cost per episode. ICD-10 codes identified a total of 11,662 adults hospitalized with RSV and 79,319 with influenza. The mean length of stay was longer for RSV than for influenza in low-risk patients aged 60–79 years, moderate-risk patients (those with chronic medical conditions) aged ≥50 years and in high-risk (those with immunocompromising conditions) patients aged