Rett syndrome is a rare hereditary disease that is one of the most common causes of intellectual disability in girls. The disease manifests itself in 6–18 months of life. Common symptoms of Rett syndrome include progressive mental and speech development delay, regression of previously acquired speech and motor skills, respiratory disorders, epilepsy, pathology of the gastrointestinal tract, endocrine, cardiovascular and urinary systems, which significantly impairs the vital functions of patients. Many children with this disease receive preventive vaccinations behind schedule or are not vaccinated at all, which is due to both refusals from parents and unjustified medical challenges from specialized specialists. The article presents a case report of a 5-year-old girl with Rett syndrome who was vaccinated later than the date indicated in the national calendar of preventive vaccinations of the Russian Federation and did not have all the necessary preventive vaccinations for her age. By contacting the Pediatrics and Child Health Research Institute in Petrovsky National Research Centre of Surgery the patient was examined by specialist specialists and referred to the Department of vaccine prevention. A serological study of the intensity of immunity to vaccine-controlled infections was conducted before and after the course of vaccinations, and an individual vaccination plan was drawn up. The department carried out immunization against chickenpox, pneumococcal and meningococcal infections, revaccination against polio, as well as vaccination against hepatitis A. In the future, a vaccination plan was drawn up for preventive vaccinations at the place of residence, and immunization of the entourage was recommended.