Active immunization of children has been proven very effective in the elimination of life-threatening complications of many infectious diseases in developed countries. However, as vaccination-preventable infectious diseases and their complications have become rare, the interest focuses on immunization-related adverse reactions. Unfortunately, fear of vaccination-related adverse effects can lead to decreased vaccination coverage and subsequent epidemics of infectious diseases. Brain disorders such as seizures or encephalopathy occur after an immunization; people (including many doctors) have a strong natural tendency to blame the vaccine. Alternative causes exist for almost all of the severe neurologic disorders that follow infant vaccinations. Neurological disorders are diseases of the brain, spine and the nerves that connect them. There are more than 600 diseases of the nervous system, such as brain tumors, epilepsy, Parkinson's disease and stroke as well as less familiar ones such as frontotemporal dementia. Neurological disorders are disorders that affect the central nervous system or the peripheral nervous systems and can impair the brain, spinal cord, peripheral nerve or neuromuscular function.