Identification of risk factors for severe respiratory syncytial virus (RSV) disease in adults could facilitate appropriate vaccine recommendations for adults. We conducted a systematic literature review (last 10 years in PubMed/Embase) to identify quantitative estimates of risk factors for severe RSV infection outcomes in high-income countries. Severe outcomes from RSV infection included hospitalization, excess mortality, lower respiratory tract infection, or a composite measure, severe RSV, which included these outcomes and others, such as mechanical ventilation and extended hospital stay. Among 1,494 articles screened, 26 met eligibility criteria. We found strong evidence that age, preexisting comorbid conditions (such as cardiac, pulmonary, and immunocompromising diseases, diabetes, and kidney disease), and living conditions (socioeconomic status and nursing home residence) increased the risk of severe outcomes. The frequency of severe outcomes among younger adults with comorbidities was generally similar to that experienced by older adults, suggesting that immunosenescence and chronic conditions are both contributing factors for elevated risk.
