Immunization is a preventive measure of the population protection from the infectious diseases. Its main goal is the prevention, suppression and eradication of infectious diseases. Although immunization has a long history, it reached its highest peak at the beginning of the 20th century. The most dangerous diseases which are prevented with immunization are infantile paralysis, diphtheria, tetanus, tuberculosis, whooping cough, smallpox, mumps, hepatitis B, diseases caused by Haemophilusom influenzae type B and measles. Before the vaccination was invented, these diseases were deadly. Child immunization is of great importance because infectious diseases are often and particularly dangerous at the age of childhood. Every country has its own compulsory immunization program and it is important to adhere to it. Today, many parents are afraid for their children's immune system after the vaccination and they are afraid of the side effects caused by the vaccines. Based on the unreliable information they get on the Internet or through the media, parents decide not to vaccinate their children. The most accurate information and answers parents can get from the doctors, the medical staff and through the education from the professional staff. The official attitude of the medicine is that the vaccines have side effects which are mild and they usually wear off spontaneously without any consequences, and only in rare cases they can be serious and leave permanent consequences; and the benefit of the vaccine application in the existing program, with all its imperfections and limitations, still surpasses the potential risks. Immunization prevents very serious diseases that can leave permanent severe consequences and can even be deadly. Vaccine denial increases the risk of child infection in case of exposure to the disease, but it also increases the risk for the whole population.