[Vaccine against COVID-19].

The COVID-19 pandemic has produced a huge health, economic and psychological collapse in our society. Health workers have had to face one of the greatest challenges in history, trying to show the population how to deal with this disease. We have learned that vaccines are the great instrument for the fight against infectious diseases and a large number of them began to appear, not as a product of chance but as a product of the enormous progress experienced in recent years with vaccines against new infectious diseases, against other diseases such as Alzheimer's and especially against cancer. All this knowledge has been applied to this disease. Practitioners lamented the little information available to them when asked questions from patients. This document wanted to be a response to these concerns, with a scientific desire, with evidence that put aside unverified data and hoaxes. Faced with an avalanche of information, most of it without the appropriate "peer review" as indicated in the introduction, any publication becomes obsolete at the time of publication, and we opted for an "online" publication, with the incorporation of versions. This online publication has been published in the documents of Spanish Society of Chemotherapy, at https://seq.es/vacunacion-covid-19. ©The Author 2021. Published by Sociedad Española de Quimioterapia. This article is distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)(https://creativecommons.org/licenses/by-nc/4.0/).