Severity of respiratory syncytial virus compared with SARS-CoV-2 and influenza among hospitalised adults ≥65 years

Introduction: Our aim was to estimate the risk of pneumonia, admission to intensive care unit (ICU) or death in individuals >= 65 years old admitted to hospital with RSV, compared to influenza or COVID-19. Methods: We included hospitalised patients from Severe Acute Respiratory Infection Surveillance in Spain between 2021-2024, aged >= 65 years, laboratory confirmed for RSV, influenza or SARS-CoV-2. Using a binomial regression with logarithmic link, we estimated the relative risk (RR) of pneumonia, ICU admission and in-hospital mortality, in patients with RSV compared to influenza or SARS-CoV-2, adjusting for age, sex, season and comorbidities. We stratified the estimates by vaccination status for influenza or SARS-CoV2. Results: Among patients unvaccinated for influenza or SARS-CoV-2, those with RSV had similar or lower risk of pneumonia [vs. influenza: RR= 0.91 (95% Confidence Interval: 0.72-1.16); vs. SARS-CoV-2: 0.81 (0.67-0.98)], ICU admission [vs. influenza: 0.93 (0.41-2.08); vs. SARS-CoV-2: 1.10 (0.61-1.99)] and mortality [vs. influenza: 0.64 (0.32-1.28); vs. SARS-CoV-2: 0.56 (0.30-1.04)]. Among the vaccinated, results were largely similar except for a higher risk of ICU admission with RSV [vs. influenza: 2.13(1.16-3.89); vs. SARSConclusions: RSV presented similar or lower intrinsic severity than influenza or SARS-CoV2. Among vaccinated patients, RSV was associated to higher ICU-admission, suggesting the potential for preventive RSV vaccination. (c) 2024 The Authors. Published by Elsevier Ltd on behalf of The British Infection Association. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).