The role of immunosenescence and chronic medical conditions on the immune response to respiratory syncytial virus in older individuals

INTRODUCTION: Respiratory syncytial virus (RSV) is an important respiratory pathogen among older adults and those with chronic conditions. We aimed to determine how host characteristics influence RSV susceptibility. METHODS: Two systematic literature reviews identified the impacts of chronic conditions on RSV infection outcomes in adults, and how immunological changes alter RSV infection susceptibility in older individuals. Searches using MEDLINE/Embase identified relevant papers published between 1 January 1990, and 2 August 2023. RESULTS: Of 4,699 records, 212 were selected. Inclusion criteria were based on relevant comorbidities, outcomes, and study methodologies. The prevalence of severe RSV-associated disease, hospitalization risk, and mortality increased with age. Contributing factors for increased RSV infection susceptibility and morbidity in adults included immunosenescence, age-related physiological function decay, and presence of certain chronic conditions. Mechanisms underlying increased RSV-susceptibility in those with chronic conditions included epithelial damage, inflammation, and direct or indirect myocardial damage. Vaccines for the prevention of RSV-associated lower respiratory disease in older adults have the potential to prevent substantial morbidity and mortality. CONCLUSIONS: Immunosenescence and chronic medical conditions increase susceptibility of adults to RSV, yet knowledge gaps remain regarding RSV pathogenesis in chronic conditions. Recently approved RSV vaccines support preventive strategies for these individuals.The protocol for this study is PROSPERO registered (identifier: CRD42021293292).