Immunization programs save millions of lives worldwide every year, protect against certain infectious diseases and possible disability as a result of illness, and directly affect the health of the individual and the overall health of the community. Continuous vaccination has led to the eradication of certain infectious diseases; some have been eliminated, while others appear very rarely. Measles today occurs sporadically in countries with high vaccination coverage, but unvaccinated people are still at risk of illness and serious complications. The importance of systematic immunization is highlighted by the whooping cough epidemic during 2023/2024 in Croatia, with 6,546 patients, which is a consequence of a cyclical increase in the number of patients as a result of weakening of immunity due to vaccination or previous illness. The health impact of infectious diseases, against which there is a possibility of vaccination, is far more serious and more likely than the possible side effects of vaccination. In Croatia, according to the official legislation, all school children are required to be vaccinated against diphtheria, tetanus, pertussis, measles, rubella, and mumps. Vaccination against human papillomavirus is still optional. Although vaccination coverage of children and youth in Croatia is relatively high, maintaining the current level of vaccination is increasingly difficult with a constant need for public health interventions aimed at promoting immunization. The concept of vaccination hesitancy is defined as delaying vaccination or refusing vaccination despite the availability of immunization. This issue undermines the efforts to reduce morbidity and mortality from vaccine-preventable diseases. A proactive and assertive approach in health promotion strategies includes individuals in an active dialogue and thus maintains optimal vaccination coverage.