This book presents studies of the main conditions that affect health and well-being of old people. Considering the present scenario of COVID-19, the effects of this viral infection on individuals older than 65 years are also discussed. The content enables professionals of health and government for the present and future actions in this important area. Readers go through  the changes occurring in organs and tissues that can interfere with susceptibility to infections, low response to vaccines, cancer, and loss of cognition during the aging process. A discussion of the central role played by the immune system in the age-related diseases and how the immunity can be impaired during the ageing process is presented. Possibilities to circumvent these conditions via healthy habits in diet, physical exercise, and new pharmacological interventions are part of the content.    This book discusses how human healthy longevity is dependent, at least inpart, of a functional immune system. Chapters were written for researchers in the field of aging and is especially suited for those interested in the study of immunosenescence and inflammaging affecting the health of old individuals.