In this talk, I will be introducing some recent work and computations on vacuum energy in quantum field theory. In the first part of the talk, I will be presenting a new view on the Casimir effect where this can be understood in terms of quantum entropy and formulated in a language close to quantum information. In the second part of the talk, I will be discussing some explicit calculations of Casimir energy in interacting quantum field theories. Both parts illustrate some unconventional - in a way that will be explained - views on the Casimir effect.