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Adverse Events Associated with Childhood Vaccines: Evidence Bearing on Causality
specific disease in question are known and aggressive surveillance of adverse events is carried out or if large controlled observational studies are done. None of this specific information is available when considering the relation between tetanus toxoid, DT, or Td and the occurrence of ADEM, transverse myelitis, or optic neuritis.
The evidence is inadequate to accept or reject a causal relation between tetanus toxoid, DT, or Td and demyelinating diseases of the CNS (ADEM, transverse myelitis, and optic neuritis).
Guillain-Barré syndrome (GBS), also known as acute inflammatory demyelinating polyneuritis, is characterized by the rapid onset of flaccid motor weakness with depression of tendon reflexes and elevation of protein levels in CSF without pleocytosis. The annual incidence of GBS appears to be approximately 1 per 100,000 for adults. The data are not definitive, but the annual incidence of GBS in children under age 5 years appears to be approximately the same. The annual incidence of GBS in children over age 5 years and teenagers appears to be lower. Chapter 3 contains a detailed description of GBS.
History of Suspected Association
Demyelinating disease of the peripheral nervous system has long been known to follow viral and some bacterial infections and can complicate the administration of live attenuated and inactivated viral vaccines. However, vaccinations are an infrequent antecedent event in patients with GBS, probably occurring in less than 1 to 5 percent of all patients. In most large case series of GBS, recent vaccination either is not mentioned or is described in only an occasional person (Hankey, 1987; Winer et al., 1988). For a more complete discussion of the history of the suspected association between vaccines and the development of GBS, see Chapter 3. A number of case reports in the medical literature have described GBS following receipt of tetanus toxoid. These are discussed in the following section.