The global rise in the older population poses novel challenges in healthcare systems. Ageing is associated with immunosenescence, a progressive decline and remodelling of the immune system, and with inflammageing, a chronic, low-grade inflammatory process. Both states are associated with increased susceptibility to infections and adverse outcomes, especially in the context of infections. In this review, we examine the molecular and cellular pathophysiological mechanisms of immunosenescence and inflammageing that predispose older adults to increased morbidity and mortality from respiratory viral infections. We also outline the clinical implications of the ageing immune system, along with the most up-to-date evidence on possible biomarkers, preventative measures and treatment options aimed at mitigating the effects of immunosenescence on the vulnerability of older adults in respiratory viral infections.