The immune system is a specialized defense system against infection. Responses to the immune system in contact with the antigen may be inherited or acquired and humoral or cellular. The born immune response, created during the fourth month of pregnancy, protects the child after the birth of the infection. This protection protect for the first three to six months of the child's life. The longer-lasting protection from infections is achieved by causing the acquired immune response by vaccination. Grafting involves lowering the antibodies in the body to induce an immune response and create immunity to the vaccine intakes. Vaccination is mandatory in Croatia and is conducted according to the vaccination program and is directed to all age groups. There are live and deadly vaccines that generate active or passive immunity. The vaccine can be either against only one cause of the disease or against several of them. By vaccinating against many disease pathogens, it wants to reduce the number of children's sting, but this can also cause unwanted reactions. In Croatia, one vaccine can be vaccinated against up to six pathogens. Apart from the vaccines themselves, and additives, added to the vaccine to create a stronger immune response, can cause allergic reactions. The organization of the vaccination program is implemented by the Croatian Institute of Public Health in cooperation with the Ministry of Health. Drug quality control is carried out by the Agency for Medicinal Products and Medical Products. Primary doctors, practitioners are vaccinations. In addition to the mandatory vaccine, vaccine can be vaccinated against other infections caused by the vaccination program as additional immunization. Contraindications for vaccination are general and specific and are determined by the vaccine. If there have been side effects in previous vaccinations, the following vaccinations will be decided by the vaccine agent in agreement with the specialist and the parents or the vaccine users.