The text discusses the history of the knowledge of infectious diseases based on the development of microbiology and immunology. The relationship and consequences of the action of the microorganism on the macroorganism, the etiology of the infectious process, and the possibilities resulting from this knowledge and the current state of the treatment of infectious diseases, but mainly their prevention, are briefly explained. The concepts of passive and active immunization, the difference between the concepts of vaccination and immunization are explained. In the booklet, you can find information about mandatory and recommended vaccination of the population in the Czech Republic and about the vaccination of travelers. Influenza is discussed in more detail, the differences in the terms epidemic and pandemic are explained, treatment options, complications of the disease and, above all, prevention with the development of vaccines and a look at the possibilities of their future development.