Children with autoimmune disease, juvenile idiopathic arthritis (JIA), receive immunomodular therapy that reduces the function of the immune response. This is why the infections, that healthy children overcome easily, can be fatal for them. Many infections can be prevented by vaccination, but there is a question of efficiency of the vaccine in an ineffective immune response. The results showed that in longer period after vaccination there was no deterioration in the JIA condition nor were there any other problems. In our study we wanted to research if the effective T cell response is formed when children with JIA receive vaccination against varicella. We isolated lymphocytes T from the peripheral blood of children whit JIA, vaccinated against varicella, and stimulated them by human herpes virus 3 (HHV-3) viral peptides. Further on, we measured, the proportions of the individual surface and intracellular markers of immune cells and cytokins with flow cytometer, and on the basis of the results, we tried to determine if there was a T cell response. Based on the results we concluded that after the vaccination of children with JIA against varicella, in most cases, an effective T cell response, which could provide protection, was formed, even in weak immune system cases. However, for a definitive confirmation of this hypothesis, a group of healthy children who have been overcome chickenpox, would be needed.