Established as a widespread public health practice in the 20th century, vaccination is one of the most important achievements in the history of the struggle to improve human health, whose effect as a technological means to prevent serious infectious diseases such as smallpox, polio, diphtheria and measles has been a milestone.

Despite its huge contribution to reducing suffering and saving lives according to the criteria of social justice, and the scientific justification, active immunisation was met with refusal from various groups right from the start. While the earlier waves of anti-vaccination activism remained fairly marginal, in the last couple of decades a new, unexpected opposition has appeared, linked to various alternative lifestyles and belief systems, with accusations that several vaccines are harmful, because they cause autism or have other bad effects on children, and suspicion that the compulsory nature of vaccination is the sign of a conspiratorial subjugation of the state to the pharmaceutical industry's need for financial gain, and so on.

As a consequence of this individualist refusal, the fall in the proportion of vaccinated people lowers the group immunity in certain communities which act as a collective barrier to the spreading of the corresponding infectious agents, thus creating a serious risk of reappearance of diseases that were eliminated long ago, even in rich countries, as is shown by the recent measles epidemic in the USA. The lecture will look at the various aspects of this problem (medical- historical, epidemiological, sociocultural, and bioethical).