  In this paper, we introduce and study an age-structured epidemiological
compartment model and its respective problem, applied but not limited to the
COVID-19 pandemic, in order to investigate the role of the age of the
individuals in the evolution of epidemiological phenomena. We investigate the
well-posedness of the model, as well as the global dynamics of it in the sense
of basic reproduction number via constructing Lyapunov functions.
