The recent discussions on the efficacy and on the alleged harms caused by Covid-19 vaccines remind us of what happened 20 years ago with the Di Bella therapy, and always with alternative therapies, re-proposing a dilemma which, with the diffusion of communications though various media, is becoming increasingly topical: who is in the position to express opinions on technical topics in the health sector, worthy of being taken into consideration? The answer seems obvious: "the experts". But who decides who the experts are, and how do you recognize them? As paradoxical as it may seem, the only practicable system is to entrust the identification of experts to the experts themselves, the only ones able to recognize who can provide reliable answers on a specific problem. It is a system with huge flaws, but which in medicine has the advantage of forcing its interpreters to deal with the consequences of their choices, thus introducing a virtuous feedback mechanism with positive effects both on the selection of experts and on the decision-making mechanisms: it is therefore a system that seems to work in the medium-long term, but which in the face of an acute crisis is of little help to those who are not experts, but need the opinion of an expert.