A wide range of studies have demonstrated that human immunity can vary significantly across demographics. In particular ageassociated declines of the immune system in older adults known as immunosenescence has become an increasingly important field of study. The impact of aging on immunity is associated with an enhanced susceptibility to both infectious and non-communicable diseases, and a substantial increase in disease severity and mortality. Immunosenescence can also limit the effectiveness of vaccines. The concept of immunosenescence is particularly relevant within the context of the COVID-19 pandemic. Age is one of the biggest risk factors for severe disease and mortality associated with SARS-CoV-2 infection, and the question of whether COVID-19 vaccines will work as well in the older adults remains an open question. Given the rapidly aging world population and the threat from both current and future pandemics, new approaches to elucidate the dynamics of immunosenescence, as well as strategies for designing vaccines that more effectively protect older adults are both urgently needed.