Vaccination is widely considered to be one of the greatest medical achievements of civilization and one of the top major breakthroughs of humanity. From an almost empirical origin of vaccinology to the present vaccinomics, our knowledge has evolved substantially and we have learnedimportant lessons. Although the main target of a vaccine is direct protection against a particular microorganism or disease, the scope of vaccination has expanded with the discovery that vaccines can also protect unvaccinated people through herd protection, or even that certain vaccines can protect against additional diseases different from those that they were designed to prevent, through so-called heterologous effects.