Age-associated changes of the immune system (immunosenescence) are contributing to increased incidence and severity of many infectious diseases in old age. They are responsible for decreased immunogenicity and clinical efficacy of many currently used vaccines in older adults. A better understanding of the basic mechanisms of immunosenescence and in-depth analysis of vaccine-induced immune responses in older adults is crucial in order to develop optimal vaccines for this age group. In addition, live-long vaccination programs and increased awareness among stakeholders and the general public are crucial for increased vaccine uptake and optimal protection of vulnerable groups