The introduction of the vaccination programme in the child population is associated with a marked decline of the morbidity and mortality of the child population, and some infectious diseases of childhood were eliminated (or eradicated). Further extension of the EPI vaccination programme as well as the perspective development of vaccines are, however, associated with some new issues and problems. The latter include the vaccination load of the child, the number of injections and thus also polyvalent vaccines. As a result of regression of infectious diseases adverse reactions come to the foreground - undesirable effects of vaccines and possibly associations with other serious diseases. The authors present contemporary knowledge and views regarding some of the mentioned problems. It is inevitable to monitor permanently positive and negative impacts of the extension of vaccination programmes. It is however important to evaluate it objectively, based on real findings, because uncritical attitudes reduce the compliance of the population as regards vaccination. It was found that the state of elimination of infectious diseases is an unstable variable and as a result of the decline of the vaccination rate local as well as extensive epidemics may develop.

        Key words: vaccination, child population, infectious diseases of childhood