The main topic of this final work is to carry out vaccination in children that will address the importance of vaccination, its effectiveness, and the parent's resistance to vaccination. A brief historical review and a definition of vaccination will be mentioned. Greater attention will be given to the immunization process, which can be carried out actively and passively, and the type of vaccine. Most infectious diseases will be infectious diseases, which are mandatory vaccination. There will also be talk about the side effects of vaccination and the most common reasons why parents express concern and rejection of vaccination. They will elaborate on the topics and the reasons for not vaccinating. Some theses will be discouraged and some will be confirmed. Everyone comes into contact with a number of causes of illness that can cause serious illnesses, damage to the body and in the most difficult cases and death, so in this paper we note the importance of the vaccine that is the greatest medical achievement of the 20th century. It has saved more lives than any other medical intervention in history. Since contagious diseases are frequent and particularly dangerous in children, vaccination of children is of great importance. In our country there is a Protocol for Mandatory Child Immunization, which includes vaccines against tuberculosis (BCG), diphtheria, tetanus and pertussis (pertussis) (DI-TEP-PER), pediatric paralysis (poliomyelitis), measles, mumps, parotitis rubella (MO-PA¬-RU) and hepatitis B and Haemophilus influenzae type b. The program is a part of primary health care for children, funded by the Croatian Institute for Health Insurance.