Susceptible individuals (yellow figurine), are exposed to viral transmission from contagious individuals (pink figurine). Once infected, a host is more or less contagious depending on the time since contamination according to distribution called the generation time (and usually parameterised using the empiric serial interval). A fraction , the value of which depends on the age of the host , will develop a critical infection and be admitted to a hospital (purple figurine) according to the complication delay distribution . The complementary fraction is assumed to recover with perfect and long-lasting immunity (green figurine). This compartment is also reachable after hospitalisation with the age-dependent probability , after the discharge delay distribution . The complementary fraction eventually dies from COVID-19. See Sofonea et al., 2021 for additional details.