This paper describes agent-based models of epidemics dynamics, willingly simplified with the goal not to predict the evolution of the epidemics, but to explain the underlying mechanisms in an interactive way. They allow to compare screening prioritization strategies, and vaccination priority strategies, on a virtual population. The models are implemented in Netlogo in two simulators, published online at https://nausikaa.net/index.php/simulating-epidemics/ to let people experiment. This paper reports on model design, implementation, and experimentations. We have compared screening strategies to assess the epidemics versus control it by quarantining infectious people; and we have compared vaccinating older people with more risk factors, versus younger people with more social contacts.