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Adverse Events Associated with Childhood Vaccines: Evidence Bearing on Causality
Measles Vaccine-Containing Preparations In an analysis of 433 spontaneous reports to a vaccine manufacturer in the Federal Republic of Germany (former West Germany) between 1976 and 1989 (Fescharek et al., 1990), 6 of 16 reports of "meningitis" or "encephalitis" were thought by the authors to be possibly related to measles, measles-mumps, or measles-mumps-rubella vaccine, leading to a rate of 1 case per 1 million doses distributed, as calculated by the authors. The vaccine strains are those currently licensed in the United States, that is, the more attenuated measles vaccine and Jeryl Lynn mumps vaccine. Assuming that all 16 reports of cases of "meningitis'' and "encephalitis" were causally related to the vaccine, the rate would increase to about 3 cases per 1 million doses distributed, which is within the range reported in other countries, as described above.
A study based on a new passive surveillance system in Canada reported a rate of 1.1 cases of meningitis or encephalitis, without distinguishing between the two, per 100,000 doses of MMR (Koch et al., 1989). (This high rate was probably due to the inclusion of meningitis in the survey.) It was estimated that more than 8 million doses of MMR were distributed in Canada during the reporting period.
A description of 212 adverse events associated with MMR reported to Swedish health authorities from 1982 to 1984 (when an estimated 700,000 doses of MMR were sold) includes 17 reports of transient, serious cases of neurologic symptoms: 3 patients with "encephalitic symptoms" who were treated at the hospital, 7 patients with "encephalitic symptoms" who were not hospitalized, 5 patients with acute symptoms with motor difficulties, 1 patient with seizures and fever, and 1 patient with hemiparesis (Taranger and Wiholm, 1987). "Encephalitic symptoms" included tiredness, whining, irritability, and mood changes with or without fever. No mention of CSF pleocytosis was made. Follow-up of at least 1 year showed that one 18-month-old boy who had developed symptoms of mild encephalitis with balance problems had residua of foot dragging and stumbling when he was tired.
Case Reports Many case reports describe encephalitis or encephalopathy following administration of measles vaccine. Because isolation of measles virus is problematic and exposure to wild-type measles virus is common, it is difficult to assess a possible role of measles or measles vaccine in the occurrence of encephalopathy or encephalitis in an individual case. Typical case reports follow.
A 5-year-old received a live measles vaccine and developed fever two weeks later (Alves et al., 1992). Three days after the onset of fever, the boy presented with hemiparesis, dysarthria, and a generalized rigid-akinetic syndrome. A spinal tap obtained four days later showed pleocytosis. One month later he was diagnosed with postencephalitic parkinsonism. He responded to levodopa therapy. The parkinsonism persisted for the 2 years